The explosion, which occurred at 10:45 am inside a seismic charge workshop of a plant owned by Poly Explosives (Jinan) Company, in Caofan township, Zhangqiu, also injured 19 people.
Thirty-four workers were in the workshop at the time of the accident that caused the building to collapse, according to a statement released by the publicity department of the Zhangqiu government.
The 19 injured workers, including two who sustained serious injuries, are being treated in local hospitals.
The three-storied workshop is in ruins following the blast. The force of explosion broke the windows of a building around 300 meters away, Xinhua reported.
According to the South China Morning Post:
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.
Industrial accidents are tragically common in China, due in part to poor industrial safety regulations and a lack of enforcement of existing regulations.