Democratic and Republican legislators yesterday intensified pressure on Attorney General Janet Reno to authorize an independent investigation of the FBI's use of incendiary devices on the day of the final assault on the Branch Davidian complex in 1993.

Congress and the Justice Department long ago concluded inquiries into the assault on the compound near Waco, Tex., but Reno last week promised a new investigation after a former senior FBI official disclosed that contrary to the FBI's denials, federal agents had fired incendiary devices a few hours before a fire consumed the Branch Davidian compound, where 76 people died.

Four members of congressional committees responsible for oversight of the Justice Department, including two Democrats who have been Reno supporters, urged an independent investigation because they believe the latest revelation has seriously damaged the department's credibility.

"The FBI had its chance to do this investigation on its own. They clearly muffed it. The only way to clear the air is to have a full, outside, independent investigation," said Sen. Charles E. Schumer (D-N.Y.), a Judiciary Committee member, on NBC's "Meet the Press."

Rep. Sheila Jackson Lee (D-Tex.), a House Judiciary Committee member, said on CNN's "Late Edition" that she supported an independent investigation to seek answers to such questions as "How were these pyrotechnic devices called for? Who gave the order? Was she [Reno] aware of it?"

Two Republicans--House Government Reform Committee Chairman Dan Burton (Ind.) and Rep. Asa Hutchinson (Ark.), a Judiciary Committee member--also urged an independent inquiry.

Hutchinson, on CNN, proposed either a commission appointed by Congress or a House-Senate committee that would not rely on the FBI to do investigative work.

Reno is said to be contemplating an independent investigation that would have either a leader or investigators from outside the Justice Department. The FBI has identified 40 agents who could do the investigation.

"At this point, the attorney general is still considering all of her options. We expect a decision shortly," said Myron Marlin, a department spokesman.

Congressional committees plan their own investigations. Burton said the Government Reform Committee has already begun an inquiry, and Senate Judiciary Committee Chairman Orrin G. Hatch (R-Utah) said he has launched another. "We're doing a total investigation of it," Hatch said on "Fox News Sunday."

The House Government Reform Committee sent investigators to Texas two weeks ago and plans to issue subpoenas this week to the Justice and Defense departments, seeking the names of personnel who were present during the 1993 assault so they can be summoned to make depositions.

For top Justice Department officials "to say that they didn't know pyrotechnic devices were used, just stretches credulity," Burton said. "It would not surprise me if Janet Reno tried to keep a lid on this because, I think, she's done that in other areas."

Hatch said: "My experience with Attorney General Reno is that she never really quite comes out in a forthright way with anything. . . . I'm real concerned about it."

No department officials appeared on network television shows to discuss the issue, but two former officials did, and they disputed Republican charges of a coverup. "This was not a coverup. This was not a grand conspiracy or anything else. What it was was a very glaring oversight" in not previously disclosing use of the incendiary devices, said Byron Sage, who was the chief hostage negotiator at the scene.

The FBI did issue a synopsis of evidence that supports its conclusion that the deadly fire was started by Branch Davidians--and that the two incendiary tear gas canisters were fired hours before the fire and at a concrete structure distant from the wooden compound.

That evidence came from infrared censors that detected fires beginning almost simultaneously in different parts of the compound, arson experts who concluded the blaze was spread by flammable fuels, survivors who reported fellow Branch Davidians started the fires and audio tapes from eavesdropping equipment on which sect members can be heard discussing setting the inferno.