HARBIN - A 57-year-old suspect died in a detention house in Northeast China's Heilongjiang province last week, after a month in custody.
The family of the deceased suspects foul play.
Police in Harbin, the provincial capital, issued a press release on Wednesday stating Wang Lijia's "death was not caused by any external force".
He was rushed to a hospital, where he died at 8 am on June 17, the police statement said.
But Wang's family is insisting he died unnaturally because his body was bruised.
"There were many visible bruises on his chest, head, left elbow and armpits," the Beijing News quoted Wang Guopeng, Wang's son, as saying.
"My father was so healthy that he managed nearly one hectare of arable land by himself," he said.
The Pinggang district police had detained Wang Lijia on May 28 on suspicion of fraud in land requisition compensation.
Wang was first held at the Pingfang detention house and later transferred to another detention house in Shuangcheng district, the release said.
Police said an autopsy was conducted on June 18, with Wang's family as witness. The result of the autopsy is expected in July.
"No evident bruises" were found on Wang's body, the police said, adding the "skin color change on Wang's chest was a consequence of pressure from medical equipment during emergency treatment".
However, prosecutors are investigating the death and the real cause would be determined once the probe is complete, the release said.
The latest custody death comes after a series of similar incidents in recent months, sparking a nationwide debate about inmates' human rights and the management of detention houses.
Most recently, 59-year-old Jiang Zengman, former director of the Wenling (Zhejiang province) tobacco monopoly bureau who was charged with bribery, collapsed during a bath at a detention house and died in a local hospital on June 6.
An autopsy conducted a day later in front of Jiang's family revealed nine broken ribs.
Late last month, inmates at a detention center in Baotou, Inner Mongolia autonomous region, thrashed a fellow inmate to death.
The deceased was put into detention at 2 am on May 29 for his involvement in a brawl. A police officer found him in the cell in a severely injured condition in the morning.
He was rushed to a hospital, where he died at 11 am.
Following the incident, three jailers and eleven inmates were handed over to the juridical and procuratorial departments for investigation.
The Ministry of Public Security (MPS) has urged detention houses to enhance their management and prevent such cases.
In a campaign to win over critics, detention centers across the country will be opened to the public from July 1, according to a statement from the MPS.
Tian Xuefei contributed to this story.