LONDON — Military engineers used a controlled explosion Friday to safely destroy a giant, rusting World War II-era bomb that was discovered during construction for the 2012 Summer Olympics, the British army said.

The 2,000-pound German bomb, which the Metropolitan Police said was the largest found in London in three decades, was uncovered last Monday as construction workers prepared a site for the games, authorities said.

If the bomb 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 officer who disabled the device 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 ones are still 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 Olympics area for the London Development Agency. Government data indicate most unexploded bombs were less than 1,000 pounds.

An average of 84 bombs that fell on civilian targets failed to explode daily during a 10-month period from September 1940 to July 1941, the government says.

Some bombs were not designed to explode on impact, but were fused with timing devices. Records indicate nearly one-fifth of those 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.