SEATTLE — The FBI’s “promising lead” in the D.B. Cooper skyjacking case has led to a man who died 10 years ago, an FBI spokesman said Monday.

FBI spokesman Fred Gutt said the bureau’s Seattle office has been investigating for more than a year a lead that has “more credibility and detail” than other tips regarding the unsolved skyjacking of a Seattle-bound flight on Thanksgiving Eve 1971. He did not identify the man.

Gutt noted there is not a lot of contradictory information that would rule out the suspect, but said that doesn’t mean the case is about to be solved.

He said the lead is one of a handful the FBI is actively pursuing in the fabled skyjacking, in which the hijacker parachuted into history from the rear of a Boeing 727 with $200,000 in cash.

FBI spokeswoman Ayn Sandalo Dietrich said Sunday that agents were investigating a “promising lead,” a day after a British newspaper reported the development in a lengthy feature story on the notorious case.

Dietrich, of the Seattle FBI office, cautioned that the bureau is not on the verge of a “big break” but is carrying out “due diligence” on the new information.

“It’s a routine part of our investigation,” she said.

Dietrich said the FBI received a tip in the past year from a member of law enforcement who directed the bureau to a credible person who might have helpful information on a suspect.

The FBI obtained an item from the person to determine if fingerprints can be extracted from it for comparison to the partial prints the hijacker left on a magazine on the plane and parts of the airliner he touched, Dietrich said.

The item has been sent to the FBI Laboratory in Quantico, Va., she said.

Asked to characterize the significance of the lead, Dietrich said, “It’s good,” but the case is “not on the brink of a solution.”

She also called the new information the “most promising lead we have right now.”

Dietrich said the FBI disclosed the information to a reporter from The Telegraph newspaper in London, but didn’t think the article was going to appear until November.

In the story, Dietrich is quoted as saying, “The credible lead is somebody whose possible connection to the hijacker is strong. And the suspect is not a name that’s come up before.”

The development is the latest in a case filled with lore, including the name D.B. Cooper, which was a media creation. The hijacker who jumped from the plane on Nov. 24, 1971, identified himself as “Dan Cooper,” but a day after the skyjacking FBI agents checked out a Portland man with the name “D.B. Cooper” and quickly cleared him. The moniker stuck, however.