A 2,000-pound bomb dropped on Japanese-occupied Hong Kong by an American bomber during World War II has been defused after it was unearthed at a construction site in the city's central Happy Valley district.

Some 2,200 Hong Kong residents were evacuated from apartment buildings around the site where the massive explosive was found. Police bomb squads moved in, carefully, to dismantle the bomb. Authorities said it was simply too big to explode in place, which is usually the safest option in such circumstances.

The weapon was identified as an AN-M66, which contains roughly 1,000 pounds of explosives. In World War II, it was considered effective against even hardened targets, such as "pillbox" or fortified gun positions, up to a 50-foot radius from the blast site. And it was lethal to infantry and light tanks up to 330 feet from where it was dropped.

The South China Morning Post says an area within 650 feet was cleared at the site on Hau Tak Lane, including the Cosmo Hotel and Cosmopolitan Hotel on Queen's Road East.

The SCMP says:

"A senior bomb disposal officer, Jimmy Yuen Hon-Wing, of the Explosive Ordnance Disposal Bureau, said a US bomber flying out of Guangzhou had carried the bomb and that it must have landed on soft ground and failed to detonate.

"Jackie Akhavan, professor of explosive chemistry at Cranfield University in Britain, said: 'It would cause a huge amount of drama. It will cause fragments and a very large blast wave.' "

Immediately after the Japanese attack on Pearl Harbor, imperial forces moved quickly to snatch up the British territories of Singapore and Hong Kong as part of a broader push to take control of Southeast Asia. After a short but spirited defense by Canadian, British and Indian troops at Hong Kong, the city fell on Christmas Day in 1941.

It seems likely that the bomb in question was dropped during one of a number of U.S. B-24 Liberator raids over Hong Kong during the war.

Copyright 2021 NPR. To see more, visit https://www.npr.org.