Story updated Dec. 7, 2011, at 4:36 a.m. EST
YOKOTA AIR BASE, Japan — Bomb experts on Wednesday detonated a 110-pound bomb found at an on-base construction site the day before.
The WWII-era explosive was left in the 10-foot deep hole it was found, covered with C-4 and then topped with dirt and other materials to absorb the impact before the modern explosives were ignited.
Seen and heard from an air-traffic control tower on the other side of the base, the explosion culminated at 2:41 p.m. in a cloud of white smoke and a low, booming thud.
Afterward the old bomb ended up a “twisted piece of metal” although it was unclear whether it exploded itself or was simply destroyed by the added munitions, said Lt. Col. Wade Rawlins, commander of the 374th Civil Engineering Squadron at Yokota.
The effort was led by an ordnance disposal team from nearby Yokosuka Naval Base, which serves all U.S. military bases in the region. Members of the crew were unavailable for comment Wednesday afternoon.
Rawlins said the response was “textbook” and without further incident.
Roads and buildings near the site that had been closed — some since Tuesday — began reopening shortly after the blast.
The emergency began Tuesday when a “suspicious object” was reported at a construction site across the street from the gym at about 1 p.m., triggering evacuations of buildings and road closures in the area.
An Air Force police officer photographed the object and sent the image to the EOD team at Yokosuka, which soon deemed it a UXO – military-speak for unexploded ordnance.
Disposing of such munitions is always executed by specialized teams, but the ability to identify them is a common skill the Air Force trains for and employs in today’s wars, Rawlins said.
“Many times an IED (in Afghanistan) is made out of an old bomb, maybe not a World War II-era bomb,” he said. But identifying old bombs and new bombs involves the same basic skill set, he said.
Officials determined the device was from WWII but have yet to figure out if it was a dud that was dropped on Yokota – a Japanese base during the war – or a training dummy, perhaps buried on purpose and forgotten until now, said Yokota spokesman Capt. Raymond Geoffroy.
Unearthing WWII bombs and other explosive is a sporadic but not uncommon occurrence in the old battlegrounds of Europe and the Pacific.
Earlier this week, officials in Germany removed a 4,000-pound bomb – believed to have been dropped by the British – in the German city of Koblenz. Nearly 45,000 residents were evacuated from the city as the bomb was removed on Sunday.