FBI agents were early today (Hong Kong time) combing the wreckage of Trans World Airlines Flight 800 to discover whether a bomb blew the plane out of the sky, killing all 228 people on board. Officials speculated on the terrorism theory after witnesses saw the Paris-bound Boeing 747-100 explode in mid-air and plummet 4,165 metres into the Atlantic Ocean minutes after take-off from New York's John F. Kennedy airport. Jack Walsh, a 747 pilot for 25 years, said: 'There was no distress call, and something the size of a 747 just wouldn't go down that quickly unless there was an explosion abroad.' But citing conflicting reports about how the aircraft went down, experts said only forensic tests on the wreckage would be able to tell for certain. 'It's too early to say precisely what happened, but it's obviously pretty rare for a plane to blow up like that in mid-flight,' said one. One of the two flight recorders, or black boxes, on the aircraft was quickly recovered from the crash site and was being taken back to the mainland to aide crash investigators, officials said. The US State Department saw no evidence of terrorism and had heard of no credible claims of responsibility, spokesman Nicholas Burns said in Washington. Attorney-General Janet Reno said a telephone caller to a television station in Tampa, Florida, had claimed responsibility. But there had been another claim of which she refused to give details. Witnesses heard a series of deafening blasts violent enough to rock small beachside towns 20 kilometres away from the crash site. They described the fiery descent of two brightly burning pieces of wreckage and more explosions as they crashed into 30 metres of water. A major rescue effort was launched within minutes of the blast, but no survivors were found. More than 100 bodies had been recovered by early today, rescuers said. No list of the nationalities of the victims was available, but 40 French nationals and 16 Pennsylvania high school students and five adults accompanying them were believed to be aboard. The plane was 25 years old - one of the oldest jumbo jets still flying - and reportedly underwent repairs on an engine pressure ratio gauge shortly before take-off, delaying its departure by one hour. The device helps set engine power. The failure of the gauge would not be sufficient to bring down the aircraft but could contribute to other problems, officials said. Dozens of grieving relatives gathered at Kennedy and Paris' Charles de Gaulle airports after hearing news of the explosion. Debris was strewn over more than two square kilometres and flames from the wreckage shot up more than 30 metres. 'We haven't even begun to look at the wreckage,' said Dennis Jones, an investigator with the National Transportation Safety Board. Rescue efforts were hampered by overcast skies, choppy seas and fog which rolled over the crash site a few hours after Flight 800 went down. Three huge C-130 transport planes parachuted divers and dropped flares over the area, and helicopter pilots used infra-red night glasses. 'We saw lots of bodies, body parts and personal effects like clothes, cartons of cigarettes and air mail, but no survivors,' said one Coast Guard officer. 'It's not a pretty sight.' Ironically, the four-man crew of one C-130 from the National Guard witnessed the crash during a routine training flight. 'We were flying off the coast at about 10 to 15 miles when we were startled by a big flash of light in the sky,' said one crewman. 'There was a huge amount of smoke. We flew over the area and could tell it was a passenger jet liner.' The crash site and nearby beaches were being treated as a crime scene, which widened as the investigation continued due to ocean currents. 'We can't rule anything out yet,' said Bob Gaffney, a councillor. 'But there is reason to believe it could be foul play. It's very suspicious and the circumstances seem to indicate a strong likelihood that this wasn't an accident.'