The explosion late Wednesday afternoon reduced part of the Yangquan Xingtong Fireworks Co. workshop - on the rural outskirts of Yangquan city - to rubble, and it was not known whether others were buried in the blast, the government's Xinhua News Agency reported.
The cause of the explosion was under investigation, and a manager of the privately run fireworks company was being held for questioning, said an officer with the police station in Yangjiazhuang town, where the factory is located. The officer gave his surname, Li, but declined to further identify himself.
Accidents in Chinese factories are common, with thousands dying every year in part because of lax enforcement of safety rules. Fireworks factories, many of them illegal, are notoriously unsafe. The day before the Yangquan blast, 13 people died in an accident in a fireworks factory in the southern province of Hunan .