The Justice Department had evidence at least four years ago that one or more potentially incendiary tear gas rounds were fired during the 1993 Waco siege, but did not provide the evidence to congressional investigators.

A 49-page FBI lab report, produced in December 1993, listed evidence from the site of the standoff and cited on its final page a "fired U.S. military 40mm shell casing which originally contained a CS tear gas round." When the Justice Department provided the report to a House panel investigating the Waco tragedy in the summer of 1995, the final page was missing, according to an internal Justice memo dated Sept. 2.

The documents provide the first evidence that the Justice Department may have been aware of the potentially incendiary tear gas rounds before the FBI's admission last month that such rounds were used. The Justice Department has repeatedly stressed that it had no knowledge of the rounds, and expressed concern that the FBI had not turned over evidence pointing to their use sooner.

The disclosure that 40mm tear gas rounds, which burn as they release gas, were used in the final assault on the Branch Davidian compound on April 19, 1993, has prompted questions about whether government agents may have helped start the fire in which about 75 sect members, including children, perished. Both the Justice Department and the FBI maintain that the rounds did not contribute to the fire.

The lab report appears to be one of thousands of pages of documents related to the Waco siege that were routinely provided to the Justice Department by the FBI. It is not clear whether the Justice Department was aware of the significance of the military tear gas round, which is not described as pyrotechnic in the report. Attorney General Janet Reno has said she was assured in briefings that no devices capable of starting a fire were used.

It is also not clear that the final page of the lab report was deliberately withheld from Congress. The Sept. 2 memo notes that although "multiple" complete copies of the report were found in Justice Department files, four copies were found that were lacking the final page. Specifically, "the page on which mention is made of a shell casing for a military CS round and the expended tear gas projectives was not produced to Congress."

Officials at both the Justice Department and the FBI said the missing page, which was provided to congressional investigators earlier this week, is a matter to be investigated by the newly appointed special counsel on Waco, former Missouri senator John C. Danforth.

Justice Department spokesman Myron Marlin said: "All I can say is whether it was an administrative error or not is something Senator Danforth could look into. But we understand the entire document including the 49th page was sent to at least one plaintiff's attorney and defense counsel in the criminal case." The criminal case against surviving Branch Davidians took place in 1994. A wrongful death suit brought against federal agencies by relatives of the dead is scheduled for trial next month.

Danforth, reached late Friday, said he could not comment. "It would create a real problem of objectivity if I were to comment on that memo," he said. "We haven't really begun the substance of the investigation so until we do I'm going to make it an objective investigation rather than commenting piecemeal on what may develop."

On Thursday, Reno appointed Danforth special counsel to investigate outstanding questions regarding Waco, including whether government officials "used any incendiary or pyrotechnic device" or "destroyed, altered or suppressed evidence or information."

Robert B. Charles, who was chief counsel for the 1995 congressional hearings on Waco and is now working for a new House inquiry being headed by Rep. Dan Burton (R-Ind.), said: "It boggles my mind that they would have withheld that from us. If you put it together with the other pieces of evidence that have come to light in the past four weeks, it suggests to me that there was a concerted effort on the part of the FBI or the Justice Department or both to cover up damning facts."

"It was the last page of the report," a Justice Department source said last night. "Sometimes the staple doesn't go all the way through and a page gets lost. I'm sure that's what happened here. There's so many rumors and innuendo floating around, something like this gets interpreted the worst way."