Chinese police have arrested six investigators from the ruling Communist Party over the death of an official who drowned when his head was plunged repeatedly into icy water, state media said.

The six investigators face a trial on charges of torturing Yu Qiyi and causing his death through intentional injury, the Beijing Times reported on Wednesday.

Yu Qiyi, a party member who was chief engineer for a state-owned firm in the eastern city of Wenzhou, died on April 9 after 38 days in detention.

Yu was detained under the controversial "shuanggui" rules for party officials and investigated for alleged irregularities in the approval of a land project, the newspaper said.

A coroner's report said he died of drowning, while photographs showed several bruises on his body.

"He had many internal and external injuries," the newspaper quoted Yu's wife, Wu Qian, as saying.

"He must have been tortured in other ways and more people may have been involved," Wu said.

"Shuanggui" is a form of investigative custody used by the Communist Party for officials accused of corruption, abuse of power and other serious disciplinary offences before the start of any legal process.

State media reported several other deaths in custody of officials in recent months, including some who were said to have jumped from windows.

During his high-profile trial last month, deposed regional leader Bo Xilai told the court that his confession was made "involuntarily" under pressure from party investigators.

Bo did not allege torture in the transcripts of his trial published online by the court, but those transcripts were censored.

Source: Agencies