Ye Xinsheng, a senior official at the prison said, "We will meet the reasonable requirements of those family members, including watching the surveillance videos, but hope they won't take extreme actions."

Ganzhou prosecutors said they will study the results of the investigation, and "if any police officers are suspected of misconduct, they will be held accountable".

Liu Renwen, a law professor at the Chinese Academy of Social Sciences, said guards in many prisons force inmates to carry out dangerous work, in same cases putting them at risk from the effects of pollution, or heavy labor.

Li Wei, of the Beijing Lawyers Association, said, "To curb such cases, prosecutors visiting prisons should perform their supervisory duties and prevent guards abusing their powers by forcing inmates to do heavy labor and beating them to death."

News of the Ganzhou Prison probe came as the Ministry of Justice announced plans to conduct a thorough investigation into illegal behavior in prisons after a series of scandals across the country last year.

Prisons will scrutinize the identities of visitors and confiscate contraband goods including drugs, cash and cellphones, and will set up a mechanism to deal with dangerous items such as weapons and explosives.

Last year's incidents included many cases where sentences were reduced illegally and a breakout at a prison in Guangdong province in November.

Last week, three guards came under investigation for suspected negligence and abuse of power after being implicated in a case involving a prisoner at Nehe Prison in Qiqihar, Heilongjiang province.

The prisoner, surnamed Wang, allegedly used a cellphone and WeChat to blackmail women living near the prison.