A U.S. Marine Corps fighter jet dropped a bomb and damaged a building in an accident at a remote military range in northern Australia (search), the government said Friday.

The bomb, dropped by an F/A-18 Hornet (search), exploded near a control tower and damaged facilities at the Delamere Air Weapons Range in the Northern Territory on Wednesday, Australia's Defense Department said. No one was injured and no details were released on the extent of the damage.

Defense Minister Robert Hill (search) said the mishap was under investigation by both Australian and American authorities.

"We certainly regard it as a serious incident," Hill told reporters in the northern city of Darwin.

Bombing exercises have ceased at the weapons range, some 80 miles south of the town of Katherine.

"Things like this will always happen; we hope not very frequently and we hope not any more dangerously," Prime Minister John Howard told Melbourne Radio 3AW. "But the idea that you can conduct any kind of military exercise without some kind of potential for mishap is unrealistic."

The U.S. Marine contingent, which is based in Japan, was conducting an annual training exercise called Southern Frontier that involves 500 troops, 15 F/A-18 Hornets and two KC-130 Hercules aircraft.

The U.S. Marine Corps said the ordnance was a 500 pound laser-guided bomb, Australian Broadcasting Corp. reported.