A disabled woman who was unable to escape her burning bedroom died yesterday morning in a fast-moving house fire in Doylestown Borough.

Brenda A. Orr, 53, who suffered from multiple sclerosis, was pronounced dead at the scene.

Orr had called 911 from her cell phone at 10:33 a.m., said Oliver Groman, spokesman for the Doylestown Fire Company.

"She said she had a fire in her bed and she was trying to put it out," Groman said. Firefighters arrived within five minutes, but the flames had grown too intense for them to rescue Orr.

"We could not advance far enough in," Groman said. "It was fully engulfed in flames."

Four firefighters, including Doylestown Borough Fire Marshal David Cell, suffered minor injuries. Cell was taken to Doylestown Hospital after a ceiling fell on him. He was treated and released; the other three were treated at the scene.

No cause was immediately determined, but investigators suspect the fire may have been caused by Orr's smoking in bed, said her mother, Martha Orr of Doylestown.

Joseph Campbell, the Bucks County coroner, said that the death had been ruled accidental, and that Orr died of smoke and soot inhalation.

He said that Orr's smoking, along with the multitude of electrical devices in the room, were among the possible causes being investigated.

The house appeared to have been largely gutted by fire before borough firefighters, assisted by neighboring fire companies, extinguished it.

Orr, who was stricken by multiple sclerosis about 15 years ago, had bought the single-story, three-bedroom house on Doyle Street in 1999.

Despite her illness, she managed to live alone with some help from caregivers, her mother said.

"Brenda was a very outgoing person who loved life and loved music," her mother said. "She would go to any musical program she could get to. And she loved her three cats."

A business graduate of Temple University, Orr had worked in management for the Southland Corp., her mother said.

Even after her illness left her homebound, she continued to do computer work for local employers, Martha Orr said.

Much of that work was done from her bedroom, her mother said, where Orr kept a computer, a television, and other electronic devices.

"I had tried to warn her about smoking, especially in bed," Martha Orr said. "We were unable to get her to quit."