Police on Thursday ruled out that Jatin Sarkar, the father of one of the victims in the Nithari mass killings, was murdered at Berhampore in Murshidabad district.

An autopsy performed established that Sarkar had drowned on September 1 while he was bathing at the Gandhi Colony ghat on the river Bhagirathi in Berhampore, Murshidabad Superintendent of Police Rahul Srivastava told PTI.

"It is clear that Sarkar's death was a case of accident and not homicide," Srivastava said.

He said doctors who performed the autospy had said that the man drowned. "We hope to get the post-mortem report by Monday," he added.

Sarkar's family members, however, were apparently not satisfied with the findings.

"We have seen the highhandedness of CBI sleuths during our stay in Delhi," Sarkar's wife Bandana said.

She also alleged that the family had received threat calls since August 28 till a few days before her husband's death.

The calls were made from two numbers -- 0120694164 and 01202501255 to his mobile, claimed Bandana.

Sarkar, one of the parents of the victims of the Nithari serial killings, had filed a petition in the court of Special CBI Judge Sapna Mishra in Ghaziabad on April 28 seeking reinvestigation of the case.