A fire swept through a two-story home early Tuesday, killing three people who had been illegally accessing electricity to power space heaters, authorities said.

One person survived the blaze by exiting an upstairs window at the home on Detroit's west side, sliding down the front porch roof and jumping to the ground, Detroit Fire Department Capt. Steve Varnas said.

Charlotte Nash said two of those killed were her brothers Marvin Allen, 62, and Tyrone Allen, 61. Lynn Greer, a 58-year-old friend of Tyrone Allen's, also was killed.

Nash said the survivor was her son, Ronald Gross, and that he was bruised but otherwise fine.

Those living in the family home had been without power for a long time because of unpaid bills and had been using electric space heaters for warmth, Nash said.

Investigators have not determined what caused the fire but found that residents had been illegally accessing electricity, Varnas said. He declined to say how they were getting electricity or whether their method could have sparked the fire.

"People struggling will try to do whatever they can," he said.

DTE Energy Co. spokesman John Austerberry said the home hasn't had utility service since July 2008. Utility workers disconnected an illegal hookup at the home in May 2009.

Austerberry said a utility worker spoke to a resident there last month about re-establishing service. The employee said it would require a $181 deposit and that hadn't been paid.

Marvin and Tyrone Allen's sister Delores Flowers said she wasn't aware of any serious financial problems facing them. They were on a fixed income but she believes they had enough money to pay their monthly utility bill.

"I don't know what happened, if it got to be too heavy," said Flowers, who lives in the Detroit suburb of Westland. "Sometimes people do not go through the proper channels ... or monitor the gas bill."

The Detroit fire was reported at about 3:30 a.m., and firefighters were at the scene when Gross jumped to safety, Varnas said. Firefighters pulled the brothers out quickly and they were taken to a nearby hospital, where they were pronounced dead. The woman's body was removed a few hours later.

He said there was no evidence of smoke detectors in the home.

"It would have been better if they had smoke detectors," Varnas said. "Sometimes you're not alerted even if it's a small fire."

Nash said her brothers used canes and walkers to get around and would have been unable to jump to safety. She said they received Social Security benefits and often called her when something was wrong.