A blast at an explosives plant in China has left 13 people dead and another 20 missing, state media said Tuesday, compounding the country's poor industrial safety record.

Another 19 people were injured in the explosion on Monday at a three-storey workshop owned by Poly Explosives (Jinan), a state-owned company in the eastern province of Shandong, the Xinhua news agency reported.

Rescuers were still searching for the missing on Tuesday but clean-up efforts had also started, the report said, citing the rescue headquarters.

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

The company is a civilian explosives manufacturer and the plant is new, with an annual output of at least 30,000 tonnes of dynamite, it added.

Safety standards are regularly flouted in China, and workplace accidents remain common despite repeated pledges by the government to improve regulations and oversight.

On April 1, an explosion in a coal mine in Jilin province in the northeast killed seven people and left 11 missing, three days after another blast at the same site left 29 workers dead.