OTTAWA - More than two decades after Air India Flight 182 was blown from the sky, a public inquiry is set to hear about a purported confession by the prime suspect in the 1985 bombing.

Talwinder Singh Parmar, head of the militant Sikh separatist group Babbar Khalsa, was arrested shortly after the attack, but the RCMP didn't have enough evidence to make any charges stick. He was freed and eventually slipped out of Canada.

There have been claims for years, however, that Parmar made a statement about the bombing -- possibly under torture or possibly in an effort to shift some of the blame to others -- before he was slain by Indian police in 1992.

The inquiry headed by former Supreme Court justice John Major is expected to start hearing evidence on the matter Monday, when two officials of the Punjab Human Rights Organization are scheduled to testify.

Their story was supposed to come out in June, when Sarabjit Singh, secretary general to the organization, and Rajvinder Singh Bains, the group's legal counsel, first journeyed to Ottawa. They were accompanied then by Harmail Singh Chandi, a former Punjab policeman said to be knowledgeable about Parmar's capture and interrogation.

The three men pulled out of the hearings and went home in June because Major couldn't give them an ironclad guarantee of anonymity. But the story leaked upon their return to India when the magazine Tehelka reported that Chandi had kept transcripts and tape recordings of the supposed confession.

Parmar was said to have confirmed he was involved in the downing of Flight 182 with the loss of 329 lives, as well as another bombing the same day that killed two baggage handlers at Narita airport in Japan.

But he was also said to have told his interrogators that the real mastermind of the plot was Lakhbir Singh Brar, a former head of the International Sikh Youth Federation who was deported from Canada as a security risk and is now believed to be living in Pakistan.

Critics in both Canada and India have questioned the claims about Brar and suggested they have more to do with internal Sikh politics than with reality. The RCMP is known to have investigated Brar in connection with the Air India bomb plot but never charged him while he was in Canada.

It's also known the Mounties have been aware for several years of the purported confession by Parmar. Members of his family say the RCMP informed them in 2002 that the force believed -- contrary to official denials from Indian authorities -- that he had been captured alive, interrogated and only then killed.

A number of RCMP witnesses are scheduled to testify this week, and they will likely be grilled on how they handled past tips about Parmar's confession. A key question will be what use Canadian investigators can make of a statement that would likely be inadmissible in a Canadian court because of suspicions that it was obtained by torture.

Rajvinder Singh Bains said in an interview in August that the Punjab Human Rights Organization conducted its own investigation of the affair, gathering information from a variety of sources. He expressed concern, however, that additional witnesses may now be unwilling to come forward because they fear for their safety in the wake of the report in Tehelka.

"So many people had promised us to give further evidence, now they'll back out," Bains told The Canadian Press from his home in India. "Nobody will talk to us."

An inquiry spokesman confirmed Sunday that Bains and Sarabjit Singh will finally testify this week, but there was no word on whether the retired policeman Chandi will return to Ottawa to join them.

There are fears, among some of the families of the Air India bombing victims, that the inquiry could be sidetracked from other important issues by the tantalizing tale of the alleged Parmar confession.

Insiders say Major is determined not to let that happen, but say he feels that he must hear evidence on the matter now that it has been brought to his attention.

Major has no mandate to lay criminal blame for the bombing, to investigate the actions of the Punjab police, or to revisit Canadian criminal prosecutions already concluded.

He has focused on issues relevant to Canadian authorities, including the turf wars between the RCMP and the Canadian Security Intelligence Service that hampered efforts to bring the Air India bombers to justice.

Only one man, Inderjit Singh Reyat, has ever been convicted in the affair. Two others, Ripudaman Singh Malik and Ajaib Singh Bagri, were acquitted a trial in Vancouver two years ago. All were associates of Parmar.