Six former investigators of the 1996 crash of TWA flight 800 from New York to Paris said on Wednesday the aircraft was brought down by an external explosion and called for the probe to be reopened.

A documentary set to air next month on the 17th anniversary of the crash that killed 230 people will "prove that the officially proposed fuel-air explosion did not cause the crash," the filmmaker said in a statement.

The six "also provide radar and forensic evidence proving that one or more ordnance explosions outside the aircraft caused the crash. They do not speculate about the source or sources of the ordnance explosions."

Numerous witnesses had reported seeing a streak of light and a fireball when the plane exploded, leading some to fear the aircraft had been struck by a rocket or missile before it came down over Long Island shortly after takeoff from John F Kennedy airport.

The National Transportation Safety Board ruled out terrorism and said the crash likely resulted from an explosion in the plane's center fuel tank due to an electrical short circuit in a fuel gauge wire aboard the Boeing 747.

The former investigators "were not allowed to speak to the public or refute any comments made by their superiors and/or NTSB and FBI officials about their work at the time of the official investigation," the filmmaker said.

"They waited until after retirement to reveal how the official conclusion by the National Traffic Safety Board (NTSB) was falsified and lay out their case in a new original documentary film."

The six are also filing a petition with the NTSB to reopen the probe.

The NTSB said in a statement it was aware of the documentary and would consider the request.

"It is our policy to give fair, thorough, and objective consideration to all petitions for reconsideration," it said, noting that a decision could come within 60 days.

"A petition for reconsideration of Board findings or a probable cause determination must be based on the discovery of new evidence or on a showing that the Board's findings are erroneous."

The NTSB described its probe as one of its "most detailed investigations," saying it lasted four years.

The documentary will air on the US television network EPIX on July 17.