An unexploded US bomb caused a minor blast at a regional Japanese airport, officials said on Wednesday, with reports saying that the device likely dated from World War II.

Footage on Japanese media showed a cloud of dust rising from a blast on a taxiway at Miyazaki Airport on the island of Kyushu. The airport in southern Japan originated in 1943 as an Imperial Japanese Navy base, sending dozens of “kamikaze” aircraft on suicide missions.

There were no reports of injuries but dozens of flights were cancelled. The airport confirmed part of a taxiway had caved in.

“After investigation with the Self-Defense Forces, we concluded that it is an explosion of a US unexploded bomb,” a transport ministry official told AFP. The official added that it was not known whether the bomb was dropped during World War II, though local media reported it likely was.

Other unexploded ordnance dropped by the United States was reportedly found at a nearby construction site in 2009 and 2011.

A total of 55 flights were cancelled, according to All Nippon Airways and Japan Airlines, affecting more than 3,400 passengers.

Top government spokesman Yoshimasa Hayashi said the airport aimed to resume operations on Thursday. “There is no threat of a second explosion, and police and firefighters are currently examining the scene,” Hayashi said.

The fire department “received a call from the airport at 7:59 am (2259 GMT Tuesday) that there was an incident involving smoke,” its spokesman told AFP.