August 24, 1996, Saturday, Late Edition - Final 

SECTION: Section 1;  Page 1;  Column 1;  Metropolitan Desk 

LENGTH: 1161 words 

F.B.I. Says 2 Labs Found Traces Of Explosive on T.W.A. Jetliner 

BYLINE:  By DAN BARRY 

DATELINE: SMITHTOWN, L.I., Aug. 23 

BODY: 
The Federal Bureau of Investigation confirmed today that its crime lab in Washington had found traces of plastic-explosive residue on a piece of wreckage from Trans World Airlines Flight 800 and said that the findings had been backed up by tests at an independent laboratory. 

James K. Kallstrom, the senior agent supervising the F.B.I.'s investigation, said the chance that the laboratory tests would be proved wrong were "slim to none." But Mr. Kallstrom also emphasized that the discovery of trace amounts of PETN, a chemical used in plastic explosives, did not conclusively prove that the Boeing 747 was downed by a bomb or a missile. He said additional evidence -- like metal fragments pitted by shock waves from a bomb blast -- would be needed before the crash could be classified as a criminal act. 

Investigators still "don't have the critical mass of information that tells us exactly what happened," Mr. Kallstrom said. "The mere fact that there are chemical traces is just not enough." 

The New York Times reported in its Friday issue that chemists in the F.B.I. laboratory in Washington had discovered traces of PETN, or pentaerythritol tetranitrate, on a piece of wreckage from the passenger cabin between rows 17 and 27, a finding that provided scientific evidence that an explosive device detonated inside the passenger cabin. Late today, two officials close to the investigation said the test result came from a piece of the floorboard from that center section of the plane. 

Law enforcement officers said it was impossible to know, for now, whether the explosion was caused by a bomb or a missile because PETN is an explosive component commonly found in both. Still, the discovery would seem to knock from contention the theory that mechanical failure caused the airplane to explode on July 17, killing all 230 aboard. 

Nevertheless, during a hastily announced news conference today, Mr. Kallstrom reiterated what has become a common refrain during the five-week investigation. "The three theories are on the board" -- a bomb, a missile or a mechanical failure could have caused the crash, he said. "When we confirm one of them, we'll take the other two off." 

Mr. Kallstrom was asked how PETN -- a powerful explosive used by commercial blasters as well as terrorists -- could have gotten onto the jetliner if not as part of a bomb or a missile. He said someone could have inadvertently brought traces of the material on board. 

"It's not inconceivable that this chemical would be available through some other means other than through an explosive device, and left on the airplane," he said. 

But on Thursday night, a senior law enforcement official laughed out loud at the suggestion of this possibility, saying investigators did not take such a scenario seriously. 

Rear Adm. Edward K. Kristensen, who is overseeing the Navy's efforts to retrieve the remaining 40 percent of the plane's wreckage from the floor of the Atlantic, said salvage workers on two Navy vessels had been careful with the debris. "There is no explosives on either the Grasp or the Grapple that could have contaminated this wreckage," he said. 

Behind all this lies another debate: whether the F.B.I. told other Federal agencies of the lab findings as soon as they were discovered -- which was as long as two weeks ago, though Mr. Kallstrom declined to give an exact date. 

At another briefing on Thursday, Mr. Kallstrom was conspicuously absent from the podium he normally shares with Robert T. Francis, vice chairman of the National Transportation Safety Board. Mr. Francis advised reporters not to attach significance to Mr. Kallstrom's absence; he said that as the head of the bureau's New York office, Mr. Kallstrom had many responsibilities outside the crash investigation. 

In fact, Mr. Kallstrom was in Washington, meeting with Attorney General Janet Reno, the F.B.I. Director, Louis J. Freeh, and other top government officials. Then at today's briefing, Mr. Kallstrom emphasized that safety board officials had been apprised of the laboratory result "as soon as we knew about it." Whether Mr. Francis, who is in charge of the overall investigation, was among those so apprised remained unclear. 

In an interview on Wednesday, Mr. Francis answered "no" when asked whether chemical residue from an explosive material had been found on airplane wreckage. Also, when asked about news reports of the positive finding during an appearance on NBC's "Today" show this morning, Mr. Francis again indicated he knew nothing about such a result. 

During today's briefing, Mr. Francis would only repeat Mr. Kallstrom's assertion that the information was shared. 

"I'm just saying what I said," he said. "That they shared it in a timely manner. I believe Mr. Kallstrom said that they shared it when they learned about it." 

Nevertheless, an element of internal intrigue hung in the air. During Thursday's briefing, Mr. Francis announced that the next briefing would be sometime next week. The safety board closed down its command post here in the Sheraton hotel, and Mr. Francis checked out of his hotel room and flew back to Washington. Then, late this morning, the safety board called the hotel to make arrangements for another news briefing -- this afternoon's. 

Mr. Kallstrom said the news briefing was called after the revelation of the discovery of chemical traces of an explosive to provide the families of the victims and others with an accurate assessment of the investigation. He also said important information had not been withheld from the public. 

"We're responsible people," he said. "Any time that we have come up with any information that we think would affect the public in general -- the traveling public specifically -- we have passed that information on to the appropriate authorities for whatever action they deemed necessary and appropriate." 

PETN is often mixed with other explosives and materials to give it plasticity, an attractive attribute for terrorists. It was a chief component in a bomb that exploded on a Pan American flight to Honolulu in 1982, and another found on a Pan Am flight two weeks later that did not explode. 

Five days after the crash of Flight 800, investigators working at an old airplane hangar in Calverton, L.I., found a trace of PETN residue in a preliminary chemical test on a piece of the right wing near where it met the fuselage. But more sophisticated testing in the F.B.I. laboratory failed to replicate the result. 

Test results like these have repeatedly frustrated investigators. But with the later tests, the F.B.I. chemists hit a forensic home run, finding conclusive evidence of PETN in wreckage from the passenger cabin. 

The location of the residue only underscored the belief by investigators that the blast occurred in this central section of the plane, probably on the right side. In addition, its location was near the right wing, where the first, inconclusive finding of PETN had been found. 

LOAD-DATE: August 26, 1996