The 2,000-pound German bomb, which the Metropolitan Police said was the largest found in London in three decades, was uncovered Monday in east London as construction workers prepared a site for the games, authorities said.
If the bomb had exploded, it would have created a large crater and sent fragments flying more than a half mile, said Maj. Matt Davies of the army's Royal Engineers. His team destroyed the bomb.
Service on two nearby subway lines was suspended Friday as a precaution while the bomb was being defused before the controlled explosion.
Davies said the bomb disposal officer who disabled the device had worked under a high level of stress.
"We're all very well trained but on something like this, where it's rusting, you can't always identify what you've got, there are so many variables," Davies said.
Nazi planes dropped thousands of bombs on east London during World War II and unexploded devices are found from time to time, particularly at construction sites.
An unexploded 2,000-pound bomb is very rare in Britain, although weapons as heavy as 4,000 pounds were dropped, according to Zetica, a consulting firm that analyzed risks in the Olympic area for the London Development Agency.
Government statistics indicate most unexploded bombs found between October 1940 and May 1941 were either 110 pounds or 550 pounds. An average of 84 bombs fell on civilian targets and failed to explode every day from Sept. 21, 1940, to July 5, 1941, government data says.
Some bombs were not designed to explode on impact, but were fused with timing devices. Records indicate nearly one-fifth of the bombs failed to explode.
Since 1955, there have been no recorded incidents of an unexploded bomb detonating in Britain, Zetica said in the report published last year.