The U.S. State Department said Monday that the Chinese government had blocked a U.S. Patent and Trademark Office employee visiting the Asian country in a personal capacity from leaving.

“We are tracking this case very closely and are engaged with Chinese officials to resolve the situation as quickly as possible,” a State Department spokesperson said.

The U.S. Patent and Trademark Office is part of the federal Department of Commerce.

The individual’s name and whether the person was detained were not disclosed.

The Chinese Embassy in Washington and the U.S. Commerce Department did not immediately respond to requests for comment.

The Washington Post reported Sunday that a U.S. citizen who works for the Commerce Department had traveled to China several months ago to visit family. The man was being prevented from leaving the country after he failed to disclose on his visa application that he worked for the U.S. government, the newspaper said, citing sources.

Beijing has used exit bans on both Chinese and foreign nationals in connection with civil disputes, regulatory enforcement and criminal investigations. Analysts say the tactic is at times used to crack down on local dissent and also as diplomatic leverage in disputes with other nations.

Washington and Beijing have had friction for years over issues ranging from tariffs to Taiwan and the origins of Covid-19.

Chenyue Mao, a Wells Fargo banker, has also been blocked from leaving China. Beijing’s foreign ministry said Monday that she was involved in a criminal case and obliged to cooperate with an investigation.

Mao is the latest of several executives from foreign corporations to be stopped as they tried to depart China.

The U.S. bank suspended all employee travel to China after Mao’s exit ban, a person familiar with the matter told Reuters last week, saying Mao was a U.S. citizen.

—REUTERS