By Lisa Lambert

WASHINGTON (Reuters) – The FBI has interviewed visa holders it believes to secretly be members of the Chinese military in more than two dozen U.S. cities, the Justice Department said on Thursday.

The department said it has arrested three Chinese nationals for visa fraud, while a fourth remains a fugitive staying at China’s consulate in San Francisco. The United States believes the four were members of China’s military posing as researchers.

“In interviews with members of the Chinese People’s Liberation Army in over 25 cities across the U.S., the FBI uncovered a concerted effort to hide their true affiliation to take advantage of the United States and the American people,” John Brown, executive assistant director of the Federal Bureau of Investigation’s national security branch, said in a statement.

Court filings show that the FBI believed the San Francisco consulate was harboring a fugitive since late June. U.S. law enforcement cannot enter a foreign embassy or consulate unless invited, and certain top officials such as ambassadors have diplomatic immunity.