Washington ? The FBI is investigating whether a dead man in the Pacific Northwest is D.B. Cooper, who hijacked a passenger jet in 1971 over Washington state and parachuted with $200,000 in ransom.

Cooper has never been found.

FBI agent Fred Gutt said Monday the bureau is following up a “credible” lead in the unsolved case and is focused on a suspect who died more than 10 years ago.

Gutt said the bureau received a tip from a retired law enforcement source about the dead man possibly being Cooper. FBI agents requested personal effects of the possible suspect, who died of natural causes.

The FBI is trying to find fingerprints or DNA on the dead man’s effects to compare with items the hijacker left behind. The FBI said three years ago that it found DNA evidence on the clip-on tie Cooper left on the plane before he jumped.

Gutt said the FBI has already tested one item of the dead man’s belongings for fingerprints. It was not conclusive. They are now working with surviving family members to gather other items for further testing.

The suspect is someone who has not been previously investigated, and Gutt said initial vetting supported the belief of the tipster. But he cautioned that the new lead may not pan out and that investigators were still pursuing other possibilities.

“Maybe this is just someone else who just happened to look like him and whose life story just kind of paralleled,” Gutt said.

Gutt said the new lead is also promising because of the way it came to the FBI. The tipster initially discussed the case with a retired law enforcement officer who then contacted the FBI. Only after the FBI contacted the witness directly did the person discuss the Cooper case with investigators.

“They’re not seeking attention,” Gutt said. “To the contrary, they’re looking to avoid it.”

Federal investigators have checked more than 1,000 leads since the suspect bailed out on Nov. 24, 1971, over the Pacific Northwest.

The man who jumped gave his name as Dan Cooper and claimed shortly after takeoff in Portland, Ore., that he had a bomb, leading the flight crew to land the plane in Seattle, where passengers were exchanged for parachutes and ransom money.

The flight then took off for Mexico with the suspect and flight crew on board. The hijacker parachuted from the plane after dark as it flew south, apparently over a rugged, wooded region of the Pacific Northwest. In 1980, a boy found several thousand dollars in $20 bills from the ransom decomposing along the Columbia River.