The last of the large metal boxes into which passenger bags had been stowed was retrieved from the sea on Sunday and appeared to be essentially intact, if somewhat battered.
James Kallstrom, the FBI agent in charge of the investigation, conceded that all four containers "are basically unremarkable".
Investigators were drawn to the theory of a bomb placed inside one of the containers in part because of a finding that the front section of the aircraft had become detached in the accident and had fallen to the ocean first. They were also attracted by parallels with the downing of Pan Am 103 over Lockerbie, Scotland, in 1988, which was traced to a bomb in the front hold.
The mystery surrounding the loss of TWA 800 therefore appears to be deepening. Investigators are far from giving up on the idea that a bomb caused the explosion, but remain unable to rule out two other possibilities: that the plane was brought down by a missile or by a mechanical failure, such as a catastrophic deployment of the engine reverse thrusters in mid-flight.
"We have these three theories and they're all on the board," Mr Kallstrom admitted. "Until we know exactly what happened and which theory proves to be the case, they'll remain there." Investigators still appear, however, to favour sabotage of some kind.
An Israeli newspaper, Maariv, reported yesterday that an FBI team is hoping to interview a Lebanese man in detention in Israel who was injured when a bomb he was making exploded prematurely in April.
Flaws in security measures at John F Kennedy airport are also coming under renewed scrutiny. These were graphically demonstrated by the findings of a local police officer investigating security arrangements a week after the crash.
With a limited-access security badge issued to ticket clerks of a commuter airline, the officer was able to penetrate any part of the airport he chose, including baggage sorting areas and parked aircraft.
"It was incredible," the officer reported, attesting about the access he gained to the aircraft themselves. "I suppose if I wanted to, I could have sat down in the pilot's seat and drove away with the thing."
Investigators in the TWA case, turning their attention away from the front cargo hold, are now questioning whether a bomb could have been placed in a food trolley or the carry-on baggage of a passenger that might have been stowed under a seat or in an overhead baggage compartment.
Interest is also being focused on the so-called centre wing fuel tank, a large tank area between the wings that was only partly filled when the plane took off. Parts of the tank already retrieved show signs of intense fire damage. If the fuel that was in the tank became warm enough to become vapour and something ignited it, it could have led to an explosion.Reuse content