The U.S. military has restricted vehicles made by the Chinese car manufacturer BYD from its sprawling Kadena Air Base in Okinawa Prefecture over security concerns about the vehicles.

The ban, which took effect Monday, currently only affects Kadena — one of the largest U.S. Air Force installations in the region.

The U.S. Forces in Japan (USFJ) did not specifically explain what prompted the move, and officials with the Kadena base did not immediately respond to a request for comment.

“Installation commanders are responsible for protecting their people, facilities, and assigned missions and may implement lawful, risk-informed security measures necessary to mitigate credible threats,” USFJ spokesperson Col. John Severns said.

The ban comes as the U.S.…