PARIS - French investigators trying to determine the cause of the Concorde crash said Friday they found a strip of metal on the runway that did not belong to the doomed aircraft.
The Accident and Inquiry Office, a branch of the French Transportation Ministry, said the strip was 16 inches long. But the office did not release any details about what the metal might have come from or what its presence might mean.
The new information was part of a statement published by investigators Friday, 10 days after one of Air France's six supersonic Concorde jetliners crashed outside Paris, killing 109 people in the plane and four on the ground. Eighty-six of the bodies have been identified.
''Having an object on the runway can be very dangerous for airplanes ... notably for the Concorde, whose tires turn at a very, very high speed,'' aviation expert Germain Chambost told French television channel LCI on Friday.
Patrick Auguin, a spokesman for France's National Union of Air Pilots, could not say whether the finding supports the theory that fragments from a burst tire pierced the aircraft's undercarriage, triggering a fire.
''If it's really a tiny piece of debris, it would seem difficult for that to have burst a tire. The tire is really very strong,'' Auguin said. Neither he nor Chambost are taking part in the investigation.
Among other new details released in the statement, investigators said one of the aircraft's tires had been changed before takeoff, and that the tire was found intact at the crash site and had not blown out.
Authorities had said earlier that at least one tire blew out during the jet's brief flight. On Friday, they said tire debris found on the runway appeared to belong to only one tire and that one scrap of tire had a large gash in it.
Tire marks on the runway indicate the aircraft veered to the left as it was cruising down the runway, investigators said in their statement. Traces of soot were also observed on the runway where the debris was found, as were parts of a water deflector and a fuel tank, the statement said.
Also Friday, Air France employees asked the airline to organize a Concorde test flight as a symbolic demonstration of the jet's reliability.
Gilles Belliard, spokesman for the National Union of Civil Aviation Mechanics, said he hoped such a flight would show there is no need to keep the luxury supersonic jet on the ground. Mechanics and other Air France employees would volunteer to board the special flight, he said.
The Transportation Ministry grounded all Air France Concorde flights following the crash, and this week it decided to keep the ban in place until experts clarify what caused the disaster.
But other types of planes have continued to fly after similar high-profile crashes, and the Air France Concorde should not be an exception, Belliard said. He noted that British Airways, the only other airline to operate Concordes, resumed its flights a day after the July 25 crash.
''There is no reason for British Airways to continue and for us not to continue,'' Belliard said.
That opinion is not universal throughout French aviation. France's National Union of Air Pilots has said it supports the ban for safety reasons.
Air France representatives could not immediately be reached for comment.