NAHA, Japan (Kyodo) -- An explosion occurred Monday at the U.S. military's Kadena Air Base in the southern Japanese prefecture of Okinawa, slightly injuring four Japanese Self-Defense Forces members who were working at a depot, local officials and the Defense Ministry said.

The ministry said the blast occurred while the SDF personnel were preparing to carry out bomb disposal operations.

According to the local officials, no evacuation order has been issued for nearby residents.

Okinawa is home to the bulk of U.S. military facilities in Japan.