The explosion took place inside a workshop of a Poly Explosives (Jinan) Co. Ltd. Plant in Caofan Township, Zhangqiu City and caused the building to collapse, state-run Xinhua news agency reported.
Thirty-four workers were in the workshop at the time of the accident.
As many as thirty-one workers have been pulled out of the rubble, including the dead. Search and rescue work for those missing is currently underway, the report said.
The injured, including two who sustained serious injuries, are being treated in local hospitals.
Covering an area of 66 hectares, the company's plant in Caofan Township was a new manufacturing base with an annual output of at least 30,000 tonnes of explosives.