Wiset Chai Chan police chief Pol Col Peerapan Janthian said the explosion was heard at about 8.50am. It happened at a three-storey shop that comprises two shophouse units selling Buddhist products.
Among the 16 people wounded, four were seriously injured. They were sent to Ang Thong Hospital.
Chaiyant Yaemklad, disaster prevention and mitigation chief of Ang Thong, said that there was one round of explosion and the noise was heard in a radius of several kilometres. A small fire also broke out but was distinguished shortly.
Deputy Ang Thong governor Panya Ngamlert said the explosion happened at Or Rungroj shop and about six units of shophouses were damaged, including a Thanachart Bank branch.
Authorities assumed later that fireworks used as bird scarers exploded in the shop.