The FBI yesterday released an infrared videotape containing a recorded conversation between two FBI agents during the final 1993 assault on the Branch Davidian compound near Waco, Tex., when a hurried and seemingly casual decision was made to use potentially incendiary military tear gas cartridges in an attempt to penetrate an underground shelter near the compound.

According to a transcript of the conversation, the early morning authorization to fire at least two such cartridges was given by Richard M. Rogers, the assistant special agent in charge of the FBI's Hostage Rescue Team. In a detailed FBI account of the tactics and equipment used during the assault, Rogers made no mention of the pyrotechnic rounds. Later, in court documents, FBI officials stated that no videotape existed of that stage of the operation.

The videotape and transcript were released as Attorney General Janet Reno continued to search for someone outside the Justice Department to head a new investigation into the fiery end to the 51-day siege. Officials said last night that some of Reno's senior aides were urging that the task be given to a prominent Republican who would enjoy bipartisan support on Capitol Hill and that at least one offer of the job was still outstanding.

The infrared videotape was shot from a surveillance aircraft early on the morning of the final assault and picked up ground radio traffic between Rogers and Stephen P. McGavin, a member of the Hostage Rescue Team. On the tape, McGavin tells Rogers that a member of his unit "thinks he can get into position with relative safety utilizing the track for cover and attempt to penetrate it [the entrance to the shelter] with military rounds."

"Of course, if there's water underneath that's just going to extinguish them, but you can try it," Rogers replied.

"He can try it?" McGavin asked.

"Yeah, that's affirmative," Rogers said.

According to the FBI, this conversation took place at 7:48 a.m. April 19, 1993, a little more than four hours before the Branch Davidian compound burst into flames. The videotape and another videotape shot later the same morning that the FBI said will be released today were among the items that the U.S. Marshals Service, acting on Justice Department orders, removed from FBI headquarters on Wednesday.

The videotape to be released today shows two military tear gas rounds being fired at the shelter by the FBI from a Bradley Fighting Vehicle that was on loan from the Army, according to a senior FBI official. The first round bounces off the roof of the shelter and detonates in a field, the official said. After considerable radio traffic with Rogers, the vehicle is then repositioned so that it can take a shot at a section of the roof made of wood. A second round is fired and successfully penetrates the shelter, the official said. The videotapes are certain to be a focal point of the new investigation that Reno has ordered into the final assault on the compound and the six years of denials by the FBI that its agents used any weapons that could have set off the blaze that claimed 76 lives.

Justice Department spokesman Myron Marlin confirmed yesterday that Reno has decided to select an "outside investigator" to head the probe. Two names that officials have confirmed were among those being considered are former Republican senators John C. Danforth (Mo.) and Warren B. Rudman (N.H.). Neither man responded to messages left with their offices yesterday.

"Her dream candidate is a middle-of-the-road Republican, a Jerry Ford Republican," said a senior Justice Department official.

Reno has acknowledged that the disclosure last week of the use of the pyrotechnic tear gas cartridges had damaged her credibility. It has also further strained the relationship between the Justice Department and the FBI and set in motion at least two planned congressional investigations.

An official said yesterday that the Justice Department was hoping to find someone to head the investigation who would provide "instant bipartisan credibility" on Capitol Hill, where criticism of the department's handling of the Waco incident and its aftermath is all but certain to intensify when Congress returns to Washington next week.

The White House yesterday continued to voice support for Reno and her decision to order U.S. marshals to enter FBI headquarters and seize the newly discovered videotapes and other evidence.

"The president is deeply concerned that the attorney general appears to have been misled and may have been lied to," said White House spokesman Jake Siewert. "She has vowed to get to the bottom of that. We fully support her effort to do that."

Rogers, the Hostage Rescue Team leader who approved use of the pyrotechnic military tear gas cartridges, was interviewed by FBI agents two days after the final assault on the Branch Davidian compound. A six-page account of the interview provides details of Rogers's actions that morning, but it deals exclusively with attempts to insert tear gas into the main compound structure and what Rogers did after the structure burst into flames. There is no mention in the account of an attempt to penetrate the underground shelter and it is not clear whether Rogers was asked about this by FBI investigators.

Last year, when ordered by a federal judge to publicly release all aerial infrared videotapes taken during the assault, FBI and Justice Department officials swore in court papers that after an exhaustive search, they could find no evidence that such recordings existed prior to 10:42 a.m.

The judge's order was in response to 1996 lawsuit over a Freedom of Information Act request filed by David T. Hardy, a Tucson lawyer who is researching a book on Waco and sued after the FBI said it would take five years to produce the material.

U.S. District Judge Alfredo C. Marquez ordered the FBI to speed up the request, and later expressed frustration when the bureau contended that no such tapes existed.

"In this court's opinion, FBI stonewalled release of [Hardy's] most controversial request: the [infrared] tapes," Marquez wrote in an order filed in July. The judge also awarded Hardy more than $32,000 in attorneys' fees, a penalty divided between the FBI and the Bureau of Alcohol, Tobacco and Firearms, whose videos and audiotapes Hardy also had sought.

FBI officials maintain that discovery of the videotape confirming use of military tear gas cartridges does not affect their contention that the fatal fire was started by Branch Davidian leader David Koresh and his followers.

They note that the underground shelter was several dozen yards away from the main compound, and that the rounds were fired more than four hours before the structure burst into flames.

Staff writer Roberto Suro contributed to this report.