An expert retained by the House Government Reform Committee said yesterday that he believes an FBI agent fired shots during the bureau's 1993 siege of the Branch Davidian compound near Waco, Tex., a view that is at odds with the FBI's consistent position that none of its agents fired at any time.

Carlos Ghigliotti, an expert in thermal imaging and videotape analysis who has done work for the FBI, said he has spent hundreds of hours reviewing various tapes of the siege, including a newly released FBI audio recording that was part of a videotape turned over to Congress recently in response to a subpoena.

Based on his review, Ghigliotti said he is convinced that during the final assault on April 19, 1993, an FBI agent shot in the direction of the Branch Davidian compound.

"I conclude that the FBI fired shots on that day," Ghigliotti said in an interview yesterday. "I conclude this based on the ground-view videotapes taken from several different angles simultaneously and based on the overhead thermal tape. The gunfire from the ground is there, without a doubt."

After being briefed yesterday by Ghigliotti, Rep. Dan Burton (R-Ind.), chairman of the committee that retained Ghigliotti as a witness, said: "What we have heard from this expert is troubling, but we think it is premature to make any final determination. We don't want to go off half-cocked. As soon as we get all the necessary information, we will hold hearings and present the information to the American people."

Ghigliotti, owner of Infrared Technologies Corp. in Laurel, said the tapes also confirm that the Davidians fired at FBI agents repeatedly during the assault. Although FBI agents were operating under rules that permitted them to return fire, bureau officials have maintained that no agents fired any shots, a position that has not changed since the day of the raid.

About 75 Branch Davidians perished in a fire that erupted during the assault. Ghigliotti is not asserting that any injuries or deaths were caused by FBI gunfire.

For years, there have been allegations that federal agents fired automatic weapons at the Branch Davidians from behind the compound, an area that was not visible to the media. These assertions were popularized in the 1997 documentary "Waco: The Rules of Engagement."

Ghigliotti said he has not arrived at any conclusion on those allegations. Rather, he has focused on three videotapes taken by news agencies that day and on the new audio tape, which is part of an FBI surveillance video.

The newly released FBI recording indicates that someone was firing shots about 12:44 p.m. and includes expressions of surprise from FBI employees circling in a plane overhead. "You can hear it," one FBI employee in the plane says of the gunfire, which federal agents believed was coming from a man with a handgun north of the compound. However, the tape does not make clear who was firing, and an FBI effort to locate the gunman was unsuccessful.

Ghigliotti said he believes the gunfire came from an FBI agent and was picked up by his microphone as he fired. He said the videotapes he reviewed show gunfire toward the compound at the time that the audio is picking up the shots. Several armored vehicles were clustered in the area of the gunfire, according to Ghigliotti.

From 1991 to 1995, Ghigliotti, 42, was paid by the FBI as a thermal imaging expert on an array of environmental dumping cases, according to an FBI document. Ghigliotti "performed reliable work for the FBI," the 1995 document states.

In 1993, Ghigliotti was sentenced to 18 months of unsupervised probation and fined $250 for assaulting the owner of a dump site. Ghigliotti, who had prepared documents for a Maryland environmental agency, alleged that the dump site owner duped him by posing as a county watchman to improperly gain access to the documents.

Ghigliotti's allegation of FBI gunfire came as former Missouri senator John C. Danforth met yesterday in Texas with attorneys for families of Branch Davidians who died in the siege, who have filed a wrongful-death suit. Danforth was appointed Waco special counsel last month by Attorney General Janet Reno, who directed him to answer a number of key questions, including whether FBI agents fired their weapons.

Michael Caddell, the lead lawyer in the $100 million wrongful-death suit, claimed that he also has new information relating to possible FBI gunfire and said that he intends to give it to Danforth. Based on clearer, newly released FBI infrared surveillance tapes, Caddell contends that there was a gun battle between Davidians and federal agents on April 19 and that gunfire was coming from at least three government positions. "Folks are shooting from both sides," he said.

FBI spokesman John Collingwood said, "We would hope in the end that both Congress and Senator Danforth will have access to every single piece of information . . . that has emerged relating to Waco. That, more than anything, will help the FBI restore its credibility on this issue."