TOKYO -- A runway at Miyazaki Airport in southwest Japan was shut down Wednesday following an early-morning explosion that damaged a section of the taxiway, local media reported.

A blast was heard on the taxiway shortly before 8 am on Wednesday as air traffic controllers saw smoke rising from the site, public broadcaster NHK reported, citing a transport ministry office at Miyazaki Airport.

Camera footage showed the blast sent fragments of the pavement and dust clouds into the air, with the hole made by the blast measuring about 7 meters long, 4 meters wide and one meter deep, according to NHK.

No one was injured and airlines said they have canceled a total of 66 flights for Wednesday.

Japan's Chief Cabinet Secretary Hayashi Yoshimasa told reporters on Wednesday afternoon that the blast was caused by a US-made bomb, assuring that there is no risk of a second explosion.

Unexploded bombs dropped by US forces during World War II have often been found at the airport.

Airport officials planned to refill the hole and resume operations on Thursday morning.