An explosion ripped through a family-owned workshop in east China's Zhejiang province on Sunday, killing 13 people and injuring 14, state media reported.

The blast in the lock-processing workshop in Wenzhou city's Ouhai district happened after sparks from a polishing machine ignited thick dust, local government officials said, according to the Xinhua news agency.

The workshop was operating illegally, the officials said.

The explosion set a fire raging across an area of two to three hundred square metres, before the flames were brought under control.

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

Nearly 50,000 people died in work-related accidents in the first nine months of 2011, according to the State Administration of Work Safety.