An investigation has begun into the sudden death of an inmate who allegedly died after being forced to take a cold shower on a chilly morning in 2008 at a labor camp in central China's Henan Province, local authorities said Tuesday.

Mu Damin, born in 1948, was detained at Kaifeng municipal labor camp for a year starting from April 25, 2007 on a robbery charge, said a spokesperson with Kaifeng Municipal Bureau of Justice.

The investigation team members were from the Discipline Inspection Commission of Kaifeng Municipal Bureau of Justice and Kaifeng Municipal Procuratorate, the spokesperson said.

Three inmates, Li Xiaoyong, Wang Debao and another one who preferred to remain anonymous, claimed that they saw Mu pass out after being forced to take a cold shower on March 14, 2008 and died after being taken to the hospital, Xiaoxiang Morning News reported on Tuesday.

"We heard that Mu died of cerebrovascular rupture," Wang said.

Mu suffered from an acute illness on March 14, 2008 and was taken to Huaihe Hospital, affiliated to Henan University. He was discharged and sent back home on March 17 and died there on March 19, said the spokesperson.

Mu was quite old and suffered from high blood pressure, so he was not assigned any work at the camp and he was granted to leave the camp 22 days before his one-year sentence ended, said the spokesperson.

Investigators would try to find out what happened and disclose their results as soon as possible. If the camp police were found to have violated relevant laws or regulations, they would be punished severely, said the spokesperson.