Forty years after a skyjacker bailed out of a passenger jet in mid-air and vanished with $200,000 in cash in one of America's enduring mysteries, police are pursuing new clues pointing to a suspect they believe is long dead.

An FBI spokesman said a source in law enforcement had directed agents to a person who was close to the suspect and had obtained objects now being analyzed to see if they bear fingerprints matching those left by the hijacker on the plane.

The spokesman, Frederick Gutt, FBI special agent in Seattle, declined to reveal the law enforcement source, the person the FBI was led to, or the deceased individual whose fingerprints are being examined.

But he said the suspect in question is someone who was not previously known to investigators.

The mysterious hijacker, given the name D.B. Cooper by the media after the incident, was dressed in a black suit and tie when he hijacked a Seattle-bound commercial flight on Thanksgiving eve 1971.

He extorted $200,000 in ransom from the airline, strapped 21 pounds of $20 bills to his body and jumped out of the plane after it took off again, apparently wearing a parachute.

He was never seen again. Many believed he had died when he bailed out of the aircraft, but no body was found.

The FBI official said that authorities had ruled out Kenny Christiansen, a former Northwest Airlines employee once suspected in the case.

"Yes, there is a lead in this matter that's being pursued," Gutt told Reuters. "It's someone who surfaced who hasn't surfaced before. It came from someone who is close to someone who is deceased. So far, we haven't been able to dismiss it."

He added: "We're seeking to compare prints and finding stuff that can add more solid evidence. We have to wait. We're still recovering some additional items. It's a process, and it's not a priority matter."

He also said the new lead, first reported over the weekend by The Telegraph newspaper in London, had originated over a year ago.