Rescuers are still searching for 20 missing people after a blast that ripped through an explosives factory in eastern China left 13 people dead and 19 others injured.

An official said Tuesday that rescuers were still searching the wreckage of the three-storey plant in Shandong province, which is operated by the state-owned company Poly Explosives, a civilian explosives manufacturer.

Police were using DNA identification to help confirm casualty numbers, said Liu Xinyun, director of the Jinan Municipal Public Security Bureau, according to Xinhua News Agency.

An official in the city of Shangqiu said he was “not sure about the cause” of the blast in the factory which produces at least 30,000 tonnes of dynamite annually.

Safety standards are regularly flouted in China and is mostly blamed for workplace accidents in the country. Pledges by the government to improve regulations and oversight has come to nothing so far, reports AFP.