A U.S. mock bomb is believed to have created this hole in Rokkasho, Aomori Prefecture, on Nov. 7. (Taiji Ito)

A U.S. F-16 fighter jet accidentally dropped a 230-kilogram mock bomb during training over private land near the Misawa Air Base in Aomori Prefecture at around 6:30 p.m. on Nov. 6, the Defense Ministry said.

The fake bomb landed 5 kilometers from the training site at the base. It did not contain explosives, and no damage was reported.

“Such an incident is a huge concern for surrounding residents and should never happen,” Chief Cabinet Secretary Yoshihide Suga said at a Nov. 7 news conference. “We urge the U.S. military to provide more information and effective measures to prevent a recurrence.”

According to the ministry, the U.S. military around 8:50 a.m. on Nov. 7 informed Japan’s Tohoku Defense Bureau that the F-16 dropped a mock bomb on a range near the base, which straddles the city of Misawa and the village of Rokkasho in the prefecture.

The U.S military later found the mock bomb buried in grass on a private farm about 5 kilometers west of the range. U.S. forces also told the ministry that they will refrain from mock-bomb drop training for the time being.