An unexploded World War II U.S. bomb buried at a Japanese airport exploded on Wednesday, causing a large crater in a runway and the cancellation of more than 80 flights but no injuries, Japanese officials said.

Land and Transportation Ministry officials said there were no planes nearby when the bomb exploded at Miyazaki Airport in southwestern Japan.

Officials said an investigation by the Self-Defense Forces and police confirmed the explosion was caused by a 500-pound U.S. bomb and there was no further threat. They determined what caused the sudden detonation.

Video taken from a nearby flight school showed the explosion sending bits of asphalt into the air like a fountain. Videos broadcast on Japanese television showed a crater in the runway that was reportedly about 7 yards in diameter and 3 feet deep.

Chief Cabinet Secretary Yoshimasa Hayashi said more than 80 flights had been canceled at the airport, which hoped to resume operations on Thursday morning.

“There is no risk of a second explosion and police and fire departments are currently investigating the scene,” Hayashi said.

A fire department “received a call from the airport at 7:59 a.m. that there had been an incident involving smoke,” its spokesman told AFP.

Miyazaki Airport was built in 1943 as a former air training area for the Imperial Japanese Navy, from which some kamikaze pilots took off for suicide attacks.

Several unexploded bombs dropped by the U.S. military during World War II were discovered in the area, according to Defense Department officials.

Additional unexploded bombs dropped by the United States were reportedly found at a nearby construction site in 2009 and 2011.

Hundreds of tons of unexploded bombs from the war remain buried across Japan and are sometimes unearthed at construction sites.

A total of 2,348 bombs weighing 41 tons were disposed of in the 2023 financial year, the Reuters news agency reported, citing the Self-Defense Force.

Last year a World War II bomb was found in England exploded what authorities are calling an “unplanned” detonation.

AFP contributed to this report.