A shopping centre construction site on Ratchawithi Road near Krung Thon Bridge was cordoned off on Monday after a cache of World War II era practice bombs was uncovered by an excavator.
Deputy national police chief Srivara Ransibrahmanakul said the 98 BDU-33 practice bombs were buried about one metre deep. They were 45 centimetres long and weighed about 11 kilogrammes each.
They were not functional and were at least 45 years old. They had not belonged to the Thai military. It was likely they had been left there by US forces after World War II, Pol Gen Srivara said.
The 6-rai construction site had been a football field. Bomb disposal experts would comb the area to ensure its safety and police would question former owners of the land, he said.
In addition to the practice bombs, five mortar shells also about 45 years old were found at the site near Sanghi intersection where the Market Place shopping centre is being built.
Pol Col Kamthorn Ouicharoen, deputy commander of the Patrol and Special Operation Division, said the practice bombs were made of cast-iron and steel and intended to be dropped from aircraft. They released a small cloud of smoke on impact to show where they landed.
They contained no explosive and the mortar rounds were also not functional, he said.
Air force spokesman AVM Pongsak Semachai said the practice munitions were made in the United States and were not in use any more.
Many more such practice bombs had previously been found buried, mostly near bridges and train stations in Bang Sue and Samsen areas, he said.