Chinese police are hunting a factory boss who enslaved mentally handicapped people, forcing them to work long hours without pay and beating them if they tried to escape

The boss of a construction materials factory in China's western Xinjiang province, hired about a dozen people, many of whom are mentally disabled, to grind rocks into powder, but did not provide clothing, pay or enough food for the workers, Chinese website tianshannet.com reported.

He disappeared before police raided the factory on Monday morning, and may have fled with the workers -- some of whom had been enslaved for up to four years -- to Chengdu city in Sichuan province, the report said. His wife was being held by police.

Incidents of forced labour have shocked China in the past, with slave bosses often preying on the mentally handicapped.

In 2007, more than 1,000 people were found working as slaves in brick kilns in Shanxi province, following a father's desperate search for his missing teenage son. The central government vowed to prevent similar offences, but cases are occasionally reported by Chinese media.

Last December, Chinese human traffickers targeted mentally disabled people from the southwestern Sichuan province countryside, luring them into dangerous employment contracts and sometimes even killing them in mine accidents for compensation.

"I have not asked the boss for the money yet," one worker who had been labouring at the factory for four years was cited by tianshannet.com as saying.

The report did not say where the workers were originally from, though it said some were confused about their backgrounds.