By the time the first officers arrived, it was too late.

The initial 911 call had been about a bus emitting flames, but those flames quickly became an inferno that consumed 24 elderly people who were being evacuated from their nursing home as this city prepared for Hurricane Rita.

Trapped by their infirmities and surrounded by flames, the residents of a facility called Brighton Gardens cried out for help in their broken down bus on Interstate 45 near Dallas, but rescuers could not reach them. Three Dallas County deputy sheriffs and a local police officer could not get past the second-level step of the bus when they arrived at 6:09 a.m.

"One deputy felt the blast furnace of flames and smelled the black acrid smoke, and he could hear them. He shined his flashlight in and said, 'Please come forward to the light. I can't get to you,' " said Dallas County Sheriff's Department spokesman Don Peritz. "Then there was a number of small explosions, and he was forced to come back off the bus."

Authorities said they believe the explosions came when some of the residents' oxygen tanks ignited.

The Brighton Gardens residents were the first of Rita's victims, dying a full 24 hours before the hurricane was to make landfall. They were among 39 residents on the bus; the 15 others were taken to Dallas hospitals. The bus driver and six nursing home employees aboard survived.

Brighton Gardens is a 140-bed assisted living and skilled nursing facility in Bellaire, a Houston suburb. It is owned by Sunrise Senior Living Inc. of McLean.

"Sunrise has been devastated by this tragedy," said Paul J. Klaassen, company chairman and chief executive officer. "Our hearts go out to the families and friends of the residents involved in this unfortunate incident. Our primary concern is for the safety of our residents, and we are shocked and saddened that this event occurred during our evacuation."

Brighton Gardens administrators began the evacuation Thursday.

Families picked up most of the residents, but two busloads of residents and staff members were dispatched to sister facilities in Dallas. One bus arrived safely early Friday. The second bus, which left Thursday night, broke down on I-45, about 20 miles south of Dallas. The driver managed to pull the vehicle onto the shoulder of the northbound lanes, to free up a lane surrounded by a sea of vehicles carrying evacuees out of Houston for as far as the eye could see.

Callers to 911 reported seeing flames coming out of the rear of the bus.

"There was heavy smoke and a lot of confusion and very elderly persons laying on the roadway -- eighties, mid-eighties, nineties," Peritz said.

By the time the flames were extinguished, the bus was a charred shell, the victims virtually destroyed.

"The majority of the bus melted. . . . In my 25 years here, I have never seen anything like this -- of this magnitude of victims -- short of an aircraft accident," Peritz said.

The National Transportation Safety Board, along with the Texas Department of Public Safety and Dallas County sheriff's office, is investigating. What sparked the initial fire is still unknown. The bus driver, employed by the charter bus company, Global Limo Inc., of Pharr, Tex., was being questioned by authorities. Officials were trying to determine who was on the bus that burned, because investigators had received only one manifest of residents' and staff members' names for the two buses that left Brighton Gardens.

Because of the intensive fire, the Dallas County medical examiner's office said some remains may have to be identified by matching DNA samples.

While authorities usually investigate the wreckage of such crashes at the scene, they moved the charred bus to a warehouse to free up the evacuation route.

Some of the Brighton Gardens residents were being evacuated -- and fleeing a hurricane -- for the second time in less than a month, said Sunrise spokesman Jamison Gosselin. But he said he did not know if any of the residents who had been evacuated from New Orleans in advance of Hurricane Katrina were on the chartered bus that caught fire Friday.

"We feel at this point that we did the best we could, and this was just a devastating and unfortunate tragedy that we never thought would have happened," Gosselin said.

Staff writer Bill Brubaker in Washington contributed to this report.

Firefighters cover the bodies of victims who were in a bus carrying elderly Hurricane Rita evacuees near Dallas.