The FBI believes that a Chinese researcher, accused of visa fraud for hiding her affiliation with the Chinese military, has been holed up in the Chinese consulate in San Francisco for a month, according to court filings, Reuters reports

The filings in U.S. District Court in San Francisco said that Tang Juan, who worked at University of California, Davis, falsely claimed on her visa application that she had not served in the Chinese military. But investigators found photos of her in a Chinese military uniform and discovered she had worked as a researcher at China’s Air Force Military Medical University.

The Federal Bureau of Investigation questioned her on June 20 and afterward she went to the consulate where the FBI believes she has remained.

She was charged with visa fraud on June 26. U.S. law enforcement cannot enter a foreign embassy or consulate unless invited, and certain top officials such as ambassadors have diplomatic immunity.

The Chinese consulate in San Francisco and Tang could not be immediately reached for comment. The U.S. State Department did not reply to a request for comment.

The news, first reported by Axios, comes as U.S.-China tensions flare, with the United States giving China 72 hours to close its consulate in Houston amid accusations of spying.

Prosecutors have argued against bail for another Chinese researcher, Chen Song, also arrested for visa fraud. Song worked at Stanford University conducting neurological research, the court filings said.

The court filings also mention two other recently charged Chinese researchers who worked at University of California, San Francisco and Duke University.

The FBI has warned universities for years about the risk of intellectual property theft by foreign researchers, and the United States has tightened restrictions on student visas as well.

Fugitive Chinese military-linked researcher Tang Juan in San Francisco consulate, US says