When a company with Chinese origins broke ground last year on a crypto-mining operation in Cheyenne, Wyo., a team at Microsoft that assesses national security threats sounded the alarm.

Not only was the site next door to a Microsoft data center that supported the Pentagon — it was about a mile away from an Air Force base that controlled nuclear-armed intercontinental ballistic missiles.

The location could allow the Chinese to “pursue full-spectrum intelligence collection operations,” the Microsoft team wrote in an August 2022 report to the Committee on Foreign Investment in the United States, a federal body that monitors threats posed by overseas investors.

Microsoft’s warning did not go unheeded. Speaking on the condition of anonymity, U.S. government officials told The New York Times last week that they had been tracking the Wyoming operation for months. One official said that measures had been taken to mitigate potential intelligence collection but declined to elaborate. In addition, the mining company said it responded to queries from the federal investment committee.

The national security concerns about the Wyoming site, previously unreported, reflect a broader unease about a recent surge in Chinese Bitcoin mines across the country.

Aside from intelligence-gathering worries, the mines, which are large warehouses or containers packed with specialized computers, put immense pressure on power grids. The computers typically run around the clock while “mining” for the digital coins, the most popular among the various cryptocurrencies.

Brian Harrell, a former assistant secretary for infrastructure protection at the Department of Homeland Security during the Trump administration, said the operations could place “enormous stress” on the grid if the mines worked in concert to wreak havoc.

Possibilities include targeted blackouts and cyberattacks.

If Chinese “infrastructure impacts key energy systems,” Mr. Harrell said, “it should immediately draw additional investigation and scrutiny.”

In at least 12 states, including Arkansas, Ohio, Oklahoma, Tennessee, Texas and Wyoming, The Times identified Chinese-owned or -operated Bitcoin mines that together use as much energy as 1.5 million homes. At full capacity, the Cheyenne, Wyo., mine alone would require enough electricity to power 55,000 houses.

Many of the mines are equipped with computers made by Bitmain, a Chinese company that has no apparent direct connection to the Chinese authorities but, according to import records, has sent some shipments to the United States through a subsidiary located at a Communist Party site in southern China.

Since Bitcoin mining was banned in China in May 2021 over concerns about energy usage and economic destabilization, Bitmain has shipped 15 times more equipment to the United States than it did in the previous five years combined, the records show. A recent presentation by the company claimed it controlled 90 percent of the global market for the equipment, which is specially designed for Bitcoin mining.

Some of the U.S. mining operations appear to be straightforward efforts by wealthy Chinese nationals to make money outside the purview of Chinese authorities. For others the ownership is opaque, while several can be traced to the Chinese government.

Court documents show the mine in Cheyenne is linked to five companies, all using the same office on Park Avenue in Manhattan. One of them is registered in the Cayman Islands and until last year was a Chinese pork-processing company. The Times did not find any links between the owners of the Cheyenne mine and the Chinese government or Communist Party.

“Microsoft has no direct indications of malicious activities by this entity,” Microsoft said in its 16-page report. “However, pending further discovery, we suggest the possibility that the computing power of an industrial-level cryptomining operation, along with the presence of an unidentified number of Chinese nationals in direct proximity to Microsoft’s Data Center and one of three strategic-missile bases in the U.S., provides significant threat vectors.”

The new risks come amid a steep rise in Bitcoin mining in the United States. Earlier this year, a Times investigation found that operations were consuming about 4,000 megawatts — enough to power over three million U.S. households — and that more megawatts were continuously coming online.

The operations’ vast energy consumption, combined with their ability to turn on or off almost instantly, is unique among large power users. The combination allows many to participate in programs that pay them to shut down when a grid is under strain.

That flexibility can help keep the lights on, but it can also disrupt the delicate balance grids require. In Texas, the state grid operator recently disclosed that some mines’ unpredictable behavior could result in “emergency conditions.”

Many mines also have digital connections with grid operators that — if inappropriately managed — could allow intrusions into critical systems.

Bitmain’s dominance of the mining machine market has raised fears. In the past, researchers found “back doors” that would have allowed the company to covertly operate its equipment. After one was discovered in 2017, the company confirmed it could have remotely controlled its mining machines. A similar issue was found in 2019. The company did not respond to questions about vulnerabilities in its devices.

In July this year, an official with the North American Electric Reliability Corporation, which oversees protection of the power grid, told Congress about the growing threat of Chinese cyberattacks. And a recent report from the Office of the Director of National Intelligence warned that if China felt a major conflict with the U.S. was imminent, “it almost certainly would consider undertaking aggressive cyber operations against U.S. homeland critical infrastructure.”

The Chertoff Group, a prominent security advisory firm, has been approached by several “critical infrastructure providers” for advice about the risks posed by Bitcoin miners, particularly those owned by the Chinese, said Ben Joelson, one of the firm’s security experts.

In many parts of the country, the frustration is palpable.

“We’re all worked up over TikTok, but nobody seems to be saying anything about these Chinese companies connecting to our grids,” said Bryan King, a Republican state senator in Arkansas whose district includes the city of Harrison, where a Chinese investment group has purchased land for a Bitcoin mine. “It just doesn’t make sense.”

Companies Within Companies

Across the United States, the identities of the Chinese mines’ owners are often hidden in a maze of shell companies that are themselves owned by shell companies. In several instances, the actual owners have ties to the Chinese Communist Party, the government or state-owned entities, records show.

In Cheyenne, a lawsuit over a disputed contract revealed that Bitmain, the Chinese computer maker, was a participant in the mine near the Air Force base. It is also involved in mining operations in Arkansas and Washington State, according to interviews and public statements.

The company’s exports to the United States have been routed over the past 15 months through a subsidiary, Hainan Bitmain Technologies, which lists its address as a Communist Party guesthouse in Wanning, a city on the eastern part of Hainan, according to records from Import Genius, a trade data aggregator.

Zhang Xinyu, an employee named as the point of contact in corporate records, said that the Bitmain subsidiary was no longer at the guesthouse, and that local governments in China vying to attract businesses offered temporary addresses so they could quickly set up shop.

“And any company can rent this location, it’s just a hotel with many rooms,” the employee added in an email. “There’s no other reason.”

But it is a very unusual arrangement. Guesthouses are typically reserved for official functions or retreats by party officials. Of the tens of millions of registered companies in China, fewer than 150 list an address at a Communist Party guesthouse, according to a search of records collected by Sayari, a company that compiles corporate information, and many of them are state-owned enterprises.

Li Jiaming, president of Bit Origin Ltd., the pork processor turned Bitcoin miner, said investors chose the site because they had secured an agreement from the local utility company to provide it with power, not because they were seeking proximity to the Microsoft data center or the missile base. “Even though we are a Microsoft neighbor and a couple of miles from the base, without power it is nothing — the business cannot succeed,” he said in an interview.

Also in Cheyenne, records show, another Chinese company involved in Bitcoin mining bought a separate plot of land near the Microsoft data center.

The company, YZY Capital Holdings, is registered at a $7.5 million condo in the TriBeCa neighborhood of Manhattan and is controlled by Yuan Qian, a Chinese businessman and Communist Party member whose biography says he has served on a government advisory panel in Wuhan. He oversees a sprawling conglomerate that owns car dealerships, a biotechnology company and financial firms.

Mr. Yuan’s company sold another lot in Cheyenne to the investment group that had raised concerns at Microsoft, according to the lawsuit. His company also owns a Bitcoin mine in eastern Oklahoma, near the small town of Oktaha. There, the local utility recently built a substation that accommodates the mine, which uses more power than 41,000 homes. In nearby Muskogee, Mr. Yuan paid nearly $2 million for a 126-acre lot. He did not respond to a request for comment.

Across the state line in Arkansas, Chinese investors operate at least three mines, with plans for several more. Outside Greenbrier, about an hour’s drive north of Little Rock, one of the mines has sparked a backlash from neighbors.

The site consists of more than 20 Antboxes, which are specialized shipping containers made by Bitmain to house hundreds of its computers. It consumes more power than the nearby town.

There are at least eight companies with ties to the site. Public records obtained by residents opposed to the mine revealed connections to a Shanghai real estate business that is nearly half-owned by the Chinese government. The company, Greenland Holdings, has more than $7 billion in investments in the United States.

The president of its U.S. subsidiary, Hu Gang, has visited Arkansas, according to records obtained by the residents. On LinkedIn, a former employee, Gloria Yao, wrote of being part of his team and scouring “over 200 target mining sites” while connecting with electric utilities and chambers of commerce in more than 10 states. The post was removed after residents began questioning the company’s motives. She declined to speak to The Times, citing a nondisclosure agreement, and Mr. Hu did not respond to requests for comment.

When Mr. Hu’s company bought land in Harrison, Ark., for another Bitcoin mine, some residents attended a contentious public meeting and asked about connections to China.

A manager at the mine in Greenbrier, Ethan Wang, took the microphone.

“I’m not a Communist,” he said, according to a video recording.

‘We Chose America’

In recent years, several states passed or proposed legislation restricting Chinese land ownership because of security concerns, but significant Bitcoin operations with Chinese ties continue to operate in some of them.

None is more prominent than Texas.

In June 2021, Gov. Greg Abbott signed the Lone Star Infrastructure Protection Act, banning companies owned by foreign adversaries from running a business that would give them access to critical infrastructure. China is the first country named as an adversary in the bill.

Days earlier, Blue Safari Group Acquisition Corp. began trading shares in New York. Its biggest shareholder, according to securities filings, was Yuet Bun Wu.

Hong Kong records show that Ms. Wu is married to a prominent businessman and political operative who serves on an advisory body to China’s legislature in Beijing. Her husband, Shie Tak Chung, has praised the Communist Party’s harsh crackdown on civil liberties in Hong Kong, and weeks after the Texas law was signed, he decried “anti-China forces in Europe and the United States.”

Blue Safari ceased to exist this April, when it merged with Bitdeer Technologies Group, one of the biggest cryptocurrency mining operations in Texas. The company is controlled by Wu Jihan, a major cryptocurrency pioneer from China and one of the original founders of Bitmain. Mr. Wu, 37, has parted ways with Bitmain and left China, setting up Bitdeer in Singapore, where he is now a citizen.

The company has a 563-megawatt operation, originally run by Bitmain, in a former aluminum-smelting plant about an hour from Austin. (It also has outfits in Tennessee and Washington State.)

Republican officials in Texas are deeply suspicious of China and its ruling party. But their embrace of Chinese-linked Bitcoin mining companies, including the largest in the United States, speaks to the deep appeal of cryptocurrencies in conservative circles, where suspicions of central banks run high.

“I want Texas to be an oasis for Bitcoin and crypto,” Senator Ted Cruz, a Republican, said at a Bitcoin conference in April, speaking broadly about the technology. “I want everyone to come to Texas.”

The state has lucrative incentives that have made it the most popular destination for Bitcoin miners in the country. One program pays cryptocurrency miners for agreeing to shut off their computers when the grid is on the brink of failure, such as during the record-breaking heat wave that hit the state this past summer. Since 2020, Bitdeer has been awarded nearly $50 million from this arrangement, according to data published by the grid operator. Those payments are subsidized by Texas ratepayers.

Responding to questions from The Times, a Bitdeer representative said the company was previously unaware of Ms. Wu’s family connection to the Chinese government. “Any indication that we are influenced by or connected to the Chinese government is false and wrong,” the representative said in an email.

Serena Shie, the daughter of Ms. Wu and Mr. Shie, said she served as an officer at Blue Safari and had used an inactive business owned by her mother to help set up acquisition companies. In an interview, she said that her parents were not engaged in the Bitcoin deal, and that she was “not even sure” they knew about it. “I don’t get involved in anything political,” she said.

The influx of mining in Texas has already begun to affect the state grid, one of the most vulnerable in the country because it is unconnected to others outside the state.

The grid’s operator, the Electric Reliability Council of Texas, recently reported that Bitcoin mines’ energy consumption and lack of transparency had resulted in forecasting errors. The mines can “magnify the severity of grid events,” impacting reliability, the company said.

One proposal to reduce this risk is to regulate how fast the mines can start or stop using energy. Unlike power generators and transmission companies, Bitcoin mines are almost wholly unregulated and operate in a “gray area,” according to Howard Gugel, a vice president at NERC, the body tasked with protecting the U.S. grid.

Chinese cryptocurrency mines have quickly entrenched themselves in Texas and are learning to adapt to its politics.

One company, Poolin, set up by a Bitmain veteran, runs a pair of mines in West Texas that together can draw on as much as 600 megawatts of energy, enough to power nearly half a million U.S. homes. The company’s founder, Kevin Pan, is a Chinese citizen who has celebrated the warm embrace he and his company have received in Texas.

At a company celebration last year, he was seen wearing a cowboy hat and challenging guests to a one-armed push-up contest.

“I feel so lucky we chose Texas,” Mr. Pan said. “We chose America.”

Julian E. Barnes contributed reporting. Video produced by James Surdam.