As far back as 1996 they knew that the center fuel tank didn't bring down TWA 800. Check here.
"Insufficient proof"
I need a more auhoratative cite than an article in the NYT dated August 1996 ... although my own views, personnally, run to another source as the initial event that brought down TWA Flt 800 ...
The captain of Eastwind flight 507 told the witness group that he had observed a “pretty bright landing light” and that he watched it “on and off for over two minutes, minimum, but I probably had seen him [the light] for over five minutes.” (From page 19 of the interview transcript, which appears as Appendix Z to the Witness Group Chairman’s Factual Report).I thnk the 'bright light' they saw was the #3 and #4 engines fodded and and issueing flames as the engines had been fodded during UAL Flt 811's event years ago were ......
The FO [First Officer of Eastwind flight 507] (witness #138) recalls that Captain David Mclaine [of Eastwind flight 507] mentioned seeing on the horizon, some fifeteen to twenty miles away, what appeared to be two landing lights. Mclaine described these lights as being very close together, causing him to think that these were the landing lights of a small aircraft such as a Lear Jet. He remained focused on the lights for what seemed to be about a minute, and then the explosion occurred. (138 stated he believes at some point after seeing these lights on the horizon, Mclaine turned on the "507's" lights to better illuminate their aircraft for other airplanes in the vicinity.)
When Mclaine later related this story to 138 and it was determined that the airplane in question turned out to be a 747 Jumbo Jet, one of the largest in the sky, 138 advised he immediately speculated that TWA 800 was already on fire before it exploded and fell from the sky. In essence, since the configuration of these lights on the horizon was very unusual, what Mclaine observed could have been the early stages of a fire aboard TWA airplane and not landing lights.