Japanese authorities detonate 30 World War II-era shells off Miyako Island, Okinawa, May 28, 2024. (Japan Maritime Self-Defense Force)

CAMP FOSTER, Okinawa — Japanese authorities safely detonated 30 shells believed to be left over from World War II this week on Miyakojima, a popular tourist destination 170 miles southwest of Okinawa’s main island.

The ordnance was discovered in December during dredging at Port Hirara, a hub for many ferries and cargo ships.

“A private contractor sweeping the site for magnetic signatures discovered the shells,” a spokesman for Miyakojima City’s Disaster Prevention and Crisis Management Division told Stars and Stripes by phone Wednesday.

The ordnance included 3-inch, 5-inch and 6-inch rounds, along with 3.1-inch mortars, a spokesman for the Japan Maritime Self-Defense Force said by phone Wednesday.

“The shells appeared to be U.S.-made,” he said. It’s customary in Japan for some government officials to speak to reporters on condition of anonymity.

Ten explosive ordnance disposal divers from JMSDF Sub Area Activity Okinawa were assigned to detonate the shells in the waters approximately a half-mile from the port, the spokesman said.

Popular tourist destinations, including Painagama and Sunayama beaches, where off-limits during the operation. Restrictions were also placed on water recreation.

The detonation was carried out at 10:30 a.m. Tuesday “without any trouble,” and all restrictions were lifted by 11:15 a.m., the city spokesman said.

Approximately 10,000 tons of ordnance were dropped on Okinawa during the Battle of Okinawa and nearly 2,000 tons remain undiscovered, according to the prefecture’s General Bureau website.

Crews disposed of nearly 15 tons between April 1, 2022, and March 31, 2023.