WACO, TEX., APRIL 19 -- The 51-day standoff with David Koresh and his cult followers culminated today in a fiery spectacle that ended with the apparent deaths of more than 80 men, women and children in what authorities said may have been a mass suicide.

Authorities said Koresh, 33, a self-styled messiah, and his Branch Davidians set their besieged compound afire this afternoon after FBI agents had knocked holes in their flimsy wooden buildings with Army combat engineer vehicles and pumped tear gas into their living quarters for six hours in an attempt to end the conflict peacefully.

Ranch Apocalypse, thought to have been filled with explosives and other ammunition, burned down within minutes.

The scene was as nightmarish as any Koresh had preached about in his doomsday vision of the world's end -- cult members in gas masks burning to death and perhaps as many as 24 children dying, maybe after being injected with poison to ease their deaths, authorities said.

"We can only assume that there was a massive loss of life," said FBI spokesman Bob Ricks.

Reporters and law enforcement officers watched in horror as flames aided by wind raced through the compound, sending huge plumes of black smoke into the air and dissolving the buildings into smoking rubble. Nine people survived, authorities said.

Authorities' most recent count of those inside was 95, including at least 25 children, although those numbers have never been confirmed. One of the survivors is a 16-year-old girl.

"I cannot tell you the horror of seeing those flames," said Ricks, who had briefed reporters during much of the seven-week standoff. "It was, 'Oh my God, they're killing themselves.' "

Many details of the final minutes of the cult members, who had held the world at bay since a Feb. 28 assault and shootout left four federal agents dead, were sketchy because the ruins remained too hot and dangerous to search, authorities said.

Agents were unable to confirm that Koresh was dead, Ricks said, but talked about him as if he had died in the fire and had ordered -- in fact desired -- the mass suicide of his followers.

"He wanted to have as many people killed as possible," Ricks said. "That's why it was called Ranch Apocalypse."

The survivors included two women and a man admitted for burn treatment at Parkland Memorial Hospital in Dallas and another woman who had a fractured ankle and minor burns and was being treated at a Waco hospital. One surviving woman has not been identified, officials said.

"We have to assume the children are all dead," Ricks said. He said an earlier report that the children were safe in an underground bunker was "one final lie on David Koresh's part."

Ricks cited speculative reports that the children had been injected with poison after the fire started but did not elaborate. Authorities had hoped that mothers would flee the compound with their young children when tear gas began pouring into the rooms. But that apparently did not happen.

The day began with federal agents hoping to smoke out Koresh, who had reneged on several past promises to surrender. Ricks said negotiators telephoned the compound early this morning, warned Steve Schneider, Koresh's second-in-command, of plans to begin pumping tear gas inside and asked the cult members to leave peacefully.

Schneider angrily slammed the phone down, Ricks said, and tossed it out the door. The Davidians remained inside, and authorities reported that about 200 rounds were fired at agents during the assault. A National Guard officer received minor injuries, Ricks said, but no one else was hurt.

At a mid-morning news conference, Ricks had described the tear-gas assault as "the next logical step in a series to bring this episode to an end." The FBI plan, he said, was to continue to gas the compound and the cult members continually today "to make their environment as uncomfortable as possible."

Late today, Attorney General Janet Reno said in Washington that "today was not meant to be D-Day. We were prepared to carry it out tomorrow and the next day and do everything we could to effect a peaceful resolution of this matter."

Ricks said after the fire that Koresh had been "continually fortifying. He was demanding provocation to get in a fight with us. . . . We believe they were preparing for another armed standoff. We frustrated that. We never shot back."

Ricks said that, when tear gas penetrated a cinderblock buffer in the compound, "the decision was made {inside} to end it . . . . Time was running out on them. . . . there was one true leader in this whole operation, and that was David Koresh."

Just after noon CDT, flames appeared in one window, at least three explosions were heard and within a half-hour, the watch tower had toppled as towering flames roared through the compound. Ricks said the Davidians used kerosene or another type of lantern fuel to ignite the blaze.

Remos Avraam, a Davidian picked up by agents in the yard, said he did not know how the fire started, Ricks said, but reported that he overheard other cult members saying, "The fire has been lit, the fire has been lit."

Fire trucks were not on the scene and did not arrive until the firestorm was well beyond control. "We cannot roll fire trucks to a scene where people could shoot them," Ricks said, citing what authorities have said was Koresh's sizable arsenal, including .50-caliber weapons.

In those final, terrible moments, according to Ricks, agents reported vivid scenes. Someone appeared on the second floor of the compound wearing a gas mask and made a throwing motion. Flames erupted, and that person signaled to agents that he did not want to be rescued. A woman in flames ran out of the building, then tried to run back in. An FBI agent grabbed her and, as she fought him, led her away from the fire.

In view of their intelligence reports, authorities said, they were not surprised that Koresh apparently chose suicide.

Two days after the February shootout, in which at least 16 federal agents were injured and as many as six cult members killed, Koresh announced for the first time that he would surrender after being allowed to broadcast his religious beliefs on a Dallas radio station.

Ricks said that, after that broadcast, Koresh attached grenades to his body, kissed the children -- many of whom he is said to have fathered -- goodbye and set out to commit suicide in front of television cameras. "But he chickened out," Ricks said.

The final showdown began at 5:55 a.m. CDT when federal agents telephoned Schneider. Five minutes later, a tank-like combat vehicle fitted with a battering ram began pounding the walls and forcing gas inside.

Army Maj. Bryan Whitman, a Defense Department spokesman, said the military had provided authorities with five M-728 combat engineer vehicles, which are based on an M-60 tank chassis. These were used to spray tear gas from pressurized dispensers mounted on a boom, he said.

Describing the warning given the Davidians, Ricks said they were advised: "This is not an assault. Do not fire. If you fire, your fire will be returned. We are introducing non-lethal tear gas. Exit the compound now and follow instructions.

"You are responsible for your own actions. Come out now, and you will not be harmed. You will be provided medical attention. Come out and you will be treated professionally. No one will be injured. Submit to proper authorities. Do not subject yourself to any more discomfort."

The adult Davidians were thought to be equipped with gas masks, perhaps capable of protecting them for as long as eight hours, but Ricks said he did not know the whereabouts of the children or whether they too were outfitted with gas masks.

Ricks stressed that the gas used was "well below lethal levels. We're using a non-pyrotechnic tear gas that does not deprive them of oxygen." He described the gas as a painful irritant that causes nausea and inflammation of mucous membranes.

By 11 a.m. CDT, he said, the cult members' only response was a banner that was unfurled outside and asked that their broken telephone be reconnected.

During the long standoff there was considerable mention of an intricate tunnel network that could be the cultists' refuge, but Ricks said authorities believed that recent rains would have flooded tunnels and that cult members had been using them to dispose of waste.

In recent weeks, federal agents had worked methodically to clear the compound of growth and vehicles to gain better access for today's assault. Ricks said Koresh became very upset, "the most violent he has acted," when tanks pulled his prized Chevrolet Camaro with a 427 cubic-inch engine from the yard Sunday.

"We treated it with care," Ricks said.

Ricks said he did not expect cult members to begin leaving the complex, despite the power of the tear gas. "This is a totally fanatical group, completely devoted to David Koresh," he said. Before the Branch Davidians emerged, Ricks said, as he had so many times in the last 51 days, they would need a signal from their leader.

Although the fire quickly devastated the compound, fire-safety experts said its size and speed were not surprising given the conditions -- steady wind and interconnected buildings made primarily of wood.

Setting such a compound on fire requires "very little sophistication," said Richard Bukowski, senior research engineer of the Building and Fire Research Laboratory at the National Institute of Standards and Technology.

An "accelerant" such as kerosene or gasoline would start a fire "that burns vigorously, burns fast, releases a lot of energy. . . . The fire gets big and can generate its own wind," he said.

The fire probably created heat in excess of 1,200 degrees Fahrenheit, Bukowski said.

"It just seems amazing that, when that fire was going, that a bunch of people just didn't break and start running," said Edward Wall, deputy administrator of the U.S. Fire Administration. "It's terrible to think about."

Garry L. Briese, executive director of the International Association of Fire Chiefs, added, "It is beyond human instinct to stay in a fire without trying to get out. That tells me that something was done to immobilize them in some way . . . something physically was keeping them there."

Briese said he doubted that anyone could have survived the fire in an underground bunker without a system that pumped in fresh air from some distance. "What we learned in places like Dresden in World War II was that the fire sucked the available oxygen away from people, and they died of suffocation," he said.

At Parkland Hospital in Dallas, Sherri Elwell, 30, of Garland, Tex., watched burn victims arriving and said, "The saddest part of it is that this satan killed all those kids. "I have four kids, and I cannot believe that a father would burn his own kids."

Elwell said she was in the emergency room with her mother when a swarm of Bureau of Alcohol, Tobacco and Firearms agents and police officers rushed into the hospital about midday.

"That's when everything started to happen," she said, noting that security officers started checking purses and bags and using metal detectors on people. From a ninth-floor hospital window, Elwell said she saw one male cult member taken from a helicopter on a stretcher into the burn unit.

The buzz of helicopters and sight of scores of security men caused chaos at the hospital, where President John F. Kennedy was taken after he was fatally shot in 1963. Many patients and visitors were not allowed to use elevators, and sections of the hospital were blocked to people without a special "permit."

"They are giving these suckers the red carpet while they're pushing me out of the way, and I'm pregnant," said Gretchen Hoenig, who said she was waiting hours in the emergency room to have a infection checked.

"An ATF officer just pushed me right out of the way," she said, explaining how she happened to be in the hallway when a cult member on a stretcher was rushed into the hospital. She said the victim's hands were wrapped in white towels or a white blanket.

Contributing to this report were staff writers Mary Jordan in Dallas and Stephen Barr, Barton Gellman, Michael Isikoff and Pierre Thomas in Washington and special correspondent Elizabeth Hudson in Austin, Tex.

The 51-day siege of David Koresh's Branch Davidian compound in Waco, Tex., ended yesterday when FBI agents injected tear gas into the buildings and Koresh followers apparently set the compound on fire. Dozens of cult members died in the blaze.

THE FINAL HOURS

(CENTRAL DAYLIGHT TIME)

6 a.m. Combat Engineer Vehicle (CEV), a modified M-60 tank, batters holes near front entrance. Boom on tank inserts tear gas into compound.

9 a.m. CEV bashes down front door of compound and wall near northwest corner, above trap door leading to bunker.

12:10 p.m. Small tongue of flame appears at southwest corner of the wooden compound.

12:20 p.m. The fire whips along west side of compound, along the men's sleeping quarters. Winds gusting to 30 mph and possibly flammable material spread by cult members speed the fire through the compound.

12:22 p.m. Federal Bureau of Investigation agents appear on ground outside main entrance.

12:24 p.m. Chinook medical evacuation helicopters fly in, land near compound.

12:25 p.m. Entire compound is in flames.

12:27 p.m. Powerful explosion, possibly of weapons or ammunition, roars up from area of weapons room. Dark, oily smoke rises 200 feet in the air.

12:30 p.m. Part of the roof collapses.

12:38 p.m. Fire trucks and ambulances arrive at the compound as the fire dies down.

HOW TEAR GAS WAS INJECTED

The tip of battering ram released tear gas after breaking through structure.

The Combat Engineer Vehicle (CEV)

Based on: M-60 battle tank.

Weight: 58 tons.

Purpose: CEV clears obstructions and can be used for close-in bombardment of hostile strong points.

Military applications: U.S. Army CEVs were used during the ground war in Operation Desert Storm to break through berms, demolish obstacles and bunkers and destroy resistance. After the cease-fire, CEVs were used to break up cinder piles that had formed around some of the burning oil wells in Kuwait, reducing a two-day job to 15 minutes.

THE SEVEN-WEEK SIEGE

Sunday, Feb. 28

9:30 a.m.: Bureau of Alcohol, Tobacco and Firearms agents move in on fortress-like compound of heavily armed religious cultists known as Branch Davidians in Waco, south of Dallas-Fort Worth. Gun battle begins.

1 p.m.: A Waco hospital confirms the death of a federal agent, the first of four.

6 p.m.: Three cult members storm out of the compound.

Deaths: Four agents (16 agents also injured), two cult members.

March 1 to April 5

Thirty-seven people, including 21 under the age of 18, leave. By cult leader David Koresh's count, 96 are still inside, including 17 under age 10. Standoff continues despite leaderUs pledge of surrender.

March 22

FBI plays chants of Tibetan monks at compound.

April 14

Koresh says siege will end when he completes manuscript on seven seals of the biblical apocalypse.

April 16 to 18

FBI agents clear ground around compound.

April 19

FBI injects tear gas into buildings; fire burns compound to the ground. Justice Department says cult members set the fire. Dozens of cultists die, including as many as two dozen children under age 18.

-- Compiled by Jeannette Belliveau and Barbara Saffir

SOURCES: Federal Bureau of Investigation, Waco Tribune-Herald via Associated Press, Washington Post research, Periscope data base, KRT Graphics