Seat of Flight 800 revealed traces of explosive

Traces of a common explosive have been found in the wreckage of TWA Flight 800, the New York Times said yesterday, further strengthening the likelihood that a bomb or a missile destroyed the Boeing 747 aircraft on 17 July, killing all 230 people aboard.

Although neither the FBI nor air-safety officials would confirm the report, the newspaper quoted three officials closely involved in the investigation as saying that traces of pentaerythritol tetranitrate (PETN), a chemical widely used in plastic explosives and missiles, had been detected in debris from the front-central part of the aircraft where the original blast occurred.

"I'm not going to comment at all," Robert Francis, the deputy chairman of the National Transportation Safety Board, said yesterday, insisting that investigators were still trying to establish the precise cause of the accident. Publicly, Mr Francis says no more than that an explosion close to the jet's central fuel tank brought about the crash. This assertion had helped keep alive the theory that vapour in the nearly empty tank caused the explosion.

But that possibility has now been all but discounted by the FBI. According to the NYT, analysis at bureau headquarters here of part of a seat from the front central area confirmed the presence of PETN more than a fortnight ago. But the news was kept secret in the hope of finding more evidence that would pin down whether a bomb or missile was responsible. Without that, no suspect could ever have been brought to trial. Further contributing to investigators' caution, no trace of the explosive has yet been found on other pieces of wreckage from the same section of the aircraft.

Assuming the PETN finding was borne out, the TWA disaster would rank as the deadliest single crime in US history, a grim distinction now held by the Oklahoma City bombing of April 1995 which killed 168 people, and before that the August 1990 arson at a Bronx social club, when 87 died.

But if it now seems virtually certain that Flight 800 was sabotaged, no firm clue has emerged as to who was responsible. No credible claims have come from any terrorists, though circumstantial links with Iranian groups have been aired in the media. The "black box" flight recorders have shown only that the sudden split-second of noise at the recording's end is "different" from the one on the recorder of the PanAm 103 blown up by a bomb in suitcase in the cargohold over Lockerbie in 1988.

Investigators have been combing the backgrounds of the victims, in case one of them might have been the target of a revenge attack.