Shu Xinhong, a mentally-challenged farmer from Yunmeng county, Hubei province, died at the end of November in an illegal tofu-making workshop in Tongzhou district - home to a large number of migrant workers. The workshop's owners had disappeared by the time the local police came to investigate on Saturday, said a police officer of the district's public security sub-bureau, who did not want to be identified.

"We arrived at 3:45 pm on Dec 3, but no one was there. The illegal workshop had closed down already," he said, adding Shu's body had been sent back to his hometown.

However, he did not give the cause of Shu's death or any updates on the investigation. He said he was unable to contact Tian Jianjun, one of the owners. Tian had told Shu Wenzhong, Shu Xinhong's father, that his son had died of a heart seizure caused by choking up at a meal, according to Beijing News.

"We'll contact the police in Shu's hometown and continue looking for workers and employers involved in this case," the unidentified police officer added.

But the police in Wuluo township of Yunmeng county, where both Tian and Shu came from, told China Daily that Shu's body had been buried a week ago by his family.

"The two families reached an agreement. Tian compensated 150,000 yuan ($ 23,190) for the death of Shu and medical fees for Yang Xiaolan, Shu Xinhong's wife who was also injured working at the illegal workshop, after the local government intervened," a police officer with the public security bureau of the county, who also refused to give his name, said.

"Shu Wenzhong and Yang Xiaolan confirmed the cause of the death as stated by Tian," the police officer said, declining to explain how Yang, also mentally-challenged, got injured in that illegal workshop. Yang had once said Tian abused her husband and herself, Beijing News reported.

"The local police wanted to conduct an autopsy, but Shu's family rejected the idea. So we respected their wish," he said, adding that the incident was now settled.

"If Beijing police asked us to investigate any further, we'll find Tian and the other people involved, even though they might have come back to Beijing," he said, ringing off immediately.

Dai Peng, dean of criminal investigation department of the Chinese People's Public Security University, said, the lack of a social security cover in many places across the country has led to rampant hiring of people with mental disabilities.

"Many local governments had no designated places to rehabilitate people with mental disabilities and didn't make use of local resources like small businesses and welfare facilities," he said.

Often family members saw mentally-challenged people as a burden, he said. "So family members often want to get rid of the 'big trouble' in their lives."

Dai also mentioned that people with mental disabilities were usually unable to report their grievances to the authorities, making the work of government watchdogs especially difficult.

Since June 2007, at least 300 people with mental disabilities were reported to have been forced to work at illegal brick kilns, coal mines and other factories across the country.