US aviation investigators stood by their verdict Tuesday that an fuel tank explosion brought down TWA Flight 800 in 1996, ahead of a documentary that revives speculation of a missile hit.

Some 230 passengers and crew died when the Boeing 747, en route to Charles de Gaulle airport in Paris, exploded in the night sky off Long Island, shortly after it took off from New York's John F. Kennedy airport.

"TWA Flight 800," a documentary to run on US cable channel Epix on July 17, the 17th anniversary of the disaster, reopens the argument that the jumbo jet was blown out of the sky by a missile.

But senior officials at the National Transportation Safety Board (NTSB) said a missile was just one of many theories that were thoroughly examined during an exhaustive four-year investigation.

"We went to the nth degree and then some," Joseph Kolly, director of the NTSB office of research and engineering, told reporters at the federal agency's training academy outside Washington.

"I'm totally convinced there was no bomb or missile," added Jim Wildey, a retired NTSB investigator who oversaw a detailed analysis of the sequence of events surrounding the disaster.

The fuselage of the ill-fated airliner, painstakingly reassembled at the NTSB academy where it now serves as a training aid, shows "no pitting, cratering, gas-washing or petalizing" -- all telltale signs of a missile strike, he said.

Streaks of light, reported by dozens of witnesses on the ground, were in fact blazing fragments of the Boeing 747 falling nearly 15,000 feet (5,000 meters) into the Atlantic Ocean, Kolly said.

Moreover, investigators conducted a raft of surface-to-air missile simulations, but concluded that it was "extremely unlikely" that Flight 800 had been hit by such a device, he added.

The NTSB maintains that TWA Flight 800 was brought down by a fuel vapor explosion, "most likely" ignited by an electrical short circuit, within an empty fuel tank between the wings and under the main passenger cabin.

Kolly did not comment on a petition now before the NTSB asking for the investigation to be reopened. The board is due to rule on the request later this summer.

But, referring to the upcoming documentary, he said: "I am upset about bringing this back up... It's just not a good thing."