(CNN) -- An unreleased documentary on the 1996 TWA Flight 800 explosion offers "solid proof that there was an external detonation," its co-producer said Wednesday.
"Of course, everyone knows about the eyewitness statements, but we also have corroborating information from the radar data, and the radar data shows a(n) asymmetric explosion coming out of that plane -- something that didn't happen in the official theory," Tom Stalcup told CNN's "New Day."
A number of people have come forward, "all saying the same thing: that there was an external force -- not from the center wing tank, there's no evidence of that -- but there is evidence of an external explosion that brought down that plane," Stalcup said.
He cited "corroborating information from the radar data" and complained that "not one single eyewitness was allowed to testify -- that's unheard of."
The film's producers are submitting a petition -- signed by "many" former investigators -- asking for the National Transportation Safety Board to reopen its investigation, based on new evidence offered by the documentary, Stalcup said.
"The family members need to know what happened to their loved ones," he said.
Asked why such information might have been suppressed, he said, "That's a question that should be answered when this investigation gets reopened."
The NTSB ruled that the explosion was caused by an electrical short circuit, most likely originating in a fuel gauge line, which found its way into the center wing fuel tank, where it detonated fuel vapors and caused the B-747 to fall in pieces into the waters off Long Island.
Skeptics have long theorized that TWA Flight 800 was brought down by sinister forces.
They include Hank Hughes, who served as a senior accident investigator with the NTSB and helped reconstruct the aircraft. Others include Bob Young, a TWA investigator who participated in the investigation, and Jim Speer, an accident investigator for the Airline Pilots Association.
"These 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," a news release announcing the documentary said.
"They waited until after retirement to reveal how the official conclusion by the (NTSB) was falsified and lay out their case."
The documentary, "TWA Flight 800," will premiere July 17, the 17th anniversary of the crash.
Stalcup is co-founder of the Flight 800 Independent Researchers Organization and has been a longtime and passionate critic of the official investigation.
Suspicions that criminals or terrorists were behind the TWA 800 explosion are not new. The FBI conducted a parallel investigation, but concluded that the incident was not a crime or terrorist attack.
The NTSB said Tuesday that it was aware of the pending release of the documentary, which will air on EPIX TV network, and of the producers' intent to file a petition to reopen the investigation.
"As required by NTSB regulation, a petition for reconsideration of board findings ... must be based on the discovery of NEW evidence or on a showing that the board's findings are erroneous," NTSB spokeswoman Kelly Nantel said in a statement. "At this point, the NTSB has not received a petition, however, we stand ready to review one, should it be filed."
Petitions are reviewed and a determination typically is made within 60 days, but the NTSB can take longer if necessary, she said. The safety board's investigation of TWA 800 lasted four years and "remains one of the NTSB's most extensive investigations," Nantel said.
Investigators "spent an enormous amount of time reviewing, documenting and analyzing facts and data, and held a five-day public hearing to gather additional facts before determining the probable cause of the accident," she said.
But her statement leaves open the possibility the case will be reopened.
"While the NTSB rarely re-investigates issues that have already been examined, our investigations are never closed, and we can review any new information not previously considered by board," it said.
The documentarians said they have a "trifecta of elements" that will "prove that the officially proposed fuel-air explosion did not cause the crash." That trifecta includes forensic evidence, firsthand sources and corroborating witnesses, and the new statements from retired investigators.
The evidence proves that "one or more ordnance explosions outside the aircraft caused the crash," the producers said. But it does not identify or speculate on the source of the ordnance explosions.
All 230 people aboard TWA 800 died when the plane, headed for Paris, exploded and crashed into the Atlantic Ocean shortly after takeoff from John F. Kennedy International Airport in New York. Scores of witnesses observed a streak of light and a fireball, giving early rise to suspicions that the terrorists had struck the plane with a rocket.
Investigators concluded the streak was likely burning fuel streaming from the plane's wing tank.