BANGOR – A passenger removed on Friday from an American Airlines trans-Atlantic flight that diverted to Bangor cleared a widely used no-fly list, but other concerns by federal authorities prompted the flight change, an airline official said Monday.

“He was not on the main list that all airlines check,” Tim Smith, American Airlines spokesman, said about the man aboard American Airlines Flight 55 from Manchester, England, that was diverted partway through its flight to Chicago. Officials from the Transportation Security Administration had the plane diverted because of threat concerns.

“The TSA obviously had other concerns from another source,” Smith said.

CBS News reported on Friday that British authorities had alerted U.S. authorities that the passenger might be on a terror watch list.

After investigating the incident, the FBI concluded that they couldn’t substantiate the threat.

“We did all the logical things we needed to do to determine that the threat was not credible,” FBI spokeswoman Gail Marcinkiewicz said Monday. “We feel that the issue has been resolved.”

Marcinkiewicz could not comment on what the threat was, but she said no charges were filed.

The plane carrying 167 passengers and 12 crew landed shortly before 1 p.m. on Friday, and one male passenger, described as being of Middle Eastern descent, was handcuffed after getting off the plane, according to witnesses.

Maine State Police with bomb-sniffing dogs and members of the Bangor Police Department’s bomb squad searched the plane and luggage, Detective Sgt. Paul Kenison, a member of the bomb squad, said Monday. “With the assistance of the state police, we searched the whole plane and the luggage and didn’t find anything,” Kenison said.

The bomb squad was at the airport for about six hours, although Kenison said that some of that time was spent awaiting orders from federal officials to go ahead with the searches.

By then, the man’s flight to Chicago already had left. A new flight crew from Boston arrived Friday evening, and by about 9 p.m. the flight resumed without the man.

As for the passenger, whose name has not been released by federal or airline officials, he remained in FBI custody until Saturday morning.

Smith said that he is not sure what happened to the man, and airport officials have referred questions to the TSA and FBI, who aren’t commenting.