U.S. Marine Corps jets accidentally fired 1,520 radioactive bullets near Okinawa during training exercises about a year ago, but the Japanese government was not informed until last Jan. 16, Foreign Ministry officials said Feb. 10.

Vice Foreign Minister Sadayuki Hayashi said the Japanese government expressed regret over the incident and the delayed information to the U.S. government. Washington said it has taken steps to prevent a repeat of such an incident, ministry officials said.

The AV-8B Harrier jets inadvertently fired 1,520 rounds of the radioactive bullets at the Tori Shima gunnery range, an uninhabited coral island 100 km from Okinawa, during training exercises in December 1995 and January 1996, according to the officials. The depleted-uranium ammunition can penetrate armored vehicles. The U.S. has collected 192 of the 1,520 bullets and cleaned the area, the officials said.

The bullets pose no threat to residents or the environment, according to U.S. surveys. Washington will periodically check the island soil, they said.

U.S. Marine Corps policy prohibits the use of the depleted-uranium ammunition on training ranges in Japan, according to ministry officials. The rounds were accidentally used because they were cataloged improperly, they said.