BANGKOK - Workers at a scrap shop in Thailand's capital accidentally detonated a large bomb believed to have been dropped during World War II, killing at least eight people and injuring 20 others, police said.

Police bomb squad chief Kamthorn Auicharoen said construction workers found the bomb buried at a building site and sold it to the scrap shop in northern Bangkok. He said workers at the shop were using a gas-powered thermal cutter to take the bomb apart when it exploded Wednesday.

Authorities initially reported seven dead, but search crews later found a child's body in the rubble, believed to be a girl about 4 years old, police Col. Virasak Phoithong said Thursday.

The massive blast ripped apart the scrap shop in Bangkok's Lad Plakao neighborhood and damaged nearby houses.

"It's likely this is a bomb dropped from a plane during World War II," Kamthorn said.

Construction workers on another project found a similar bomb in a different area of Bangkok this past Saturday, but it was safely handed over to police explosive experts.

Bangkok was bombed by US and British planes during World War II, when it was occupied by Japanese forces and served as a hub for their campaign in Southeast Asia. Buried bombs from the era continue to be found from time to time in other major Asian cities, including Hong Kong and Singapore.