By the time firefighters arrived — just three minutes and 27 seconds after the first 911 call — the flames were shooting up the Bronx building’s wooden stairwell like a “blowtorch,” fire officials said yesterday. After two hours of burning, the death toll was higher than family members, neighbors, and the city could bear: Eight children and one mother had perished in the three-alarm fire.

Fire marshals said the fire was started by an overheated space heater that ignited a mattress in a bedroom on the ground floor.

A woman sleeping in the bedroom woke up to the smoke sometime before 11 p.m. on Wednesday and immediately fled upstairs with her 5-year-old child. Instead of calling 911, she recruited other members of the household to fight the fire. Officials pointed to that decision and the fact that she didn’t close the door behind her as reasons firefighters, despite a remarkable response time, couldn’t rescue more people.

“Seconds count in something like this,” Mayor Bloomberg said. “Closing the door would have given everybody in this building a much better chance to escape.”

The fire was driven up the stairs by wind coming through a back door and broken windows in what the chief of the fire department, Salvatore Cassano, described as a “chimneylike effect.” The fire was doubling itself every 30 seconds during the worst part of the blaze, he said. Two smoke detectors were in the building, but they had no batteries.

Officials said 22 people, all of them immigrants from the West African nation of Mali, lived in the four-story building located blocks away from Yankee Stadium in the Highbridge section of the Bronx. Seventeen of the residents were children.

Mamadou Soumare, who was driving a livery cab at 139th Street and Amsterdam Avenue, received a frantic call from his wife, who said there was a fire in their home. A neighbor made the first 911 call at 11:07 p.m., and firefighters were on the scene by 11:10 p.m., Chief Cassano said. Still, the fire was already well developed and many of the household’s children were trapped on the upper floors.

“They allowed it to build up for awhile, in my mind,” one of the first firefighters to arrive on the scene, Lieutenant Larry Lanza, said. Inside, it was “black to the floor,” meaning zero visibility, he said.

When Mr. Soumare arrived, there was nothing he could do. His wife, Fatoumata, 42, was later found dead in a front bedroom on the fourth floor of the building. His 3-year-old son, Djibril, and twin six-month-old daughters, Sisi and Harouma, still in their cribs, were found dead. Three of his children survived.

“I don’t know what I’m going to do,” Mr. Soumara said in an interview with the Associated Press yesterday. “She said, ‘We have a fire.’ She was screaming.”

Before firefighters arrived on the scene, Edward Soto, 28, and David Todd, 40, were sitting in the living room of a neighboring building playing a video game. Someone knocked on the door, saying there was a fire, and within a minute they were sprinting over a fence to the backyard of the burning building.

Through the smoke, Mr. Soto said he could see a woman leaning out a second-floor window with a child dangling from her arms. Mr. Todd yelled out: “Throw them down.”

Mr. Soto and another man, Hector Ortiz, caught the first child, a boy, but a second child came down too quickly and landed on an abandoned bathtub. The mother came down a moment later and hit the concrete.

“She was screaming, ‘My babies, my babies,’ and then she hit the ground and she was silent,” Mr. Soto said.

That woman and the two children were still alive as of last night. They could not immediately be identified.

Excluding the September 11, 2001, terrorist attacks, the fire had the most fatalities of any in the city since the Happy Land fire in 1990, which killed 87 people trapped in a Bronx social club. Chief Cassano said he couldn’t recall a fire that claimed the lives of so many children.

A father of five of the victims, Moussa Mougassa, was returning from a business trip in Mali yesterday after hearing the news of his family’s devastating loss. The Mougassa children who died were identified as Bandiougou, 11, Mahamadou, 7, Abuducary, 6, Diaba, 3, and Bilaly, 1. Six of his children and his wife survived.

All of the victims died of smoke inhalation, a spokeswoman for the Medical Examiner’s Office, Ellen Borakove, said. There were 19 total injuries, including four firefighters and a paramedic. A 7-year-old child was in critical condition last night. Four other children were in the hospital in improving conditions.

The ambassador who leads Mali’s Permanent Mission to the United Nations, Cheick Sidi Diarra, said some of the victims would be repatriated to Mali for burial. Along with local donations, the mission has asked the national government for help in sending the remains home, he said.

“They were totally under shock,” he said of the families of the victims. “But at the same time, they were comforted by the pooling of support that has been shown by the community.”

Some of the children attended P.S. 73. The president of the school’s Parent Teacher Association, Irma Belcore, said the children from the two families tended to go about in groups and spent a lot of time riding their bicycles.

“You never see just one of them,” she said. “They stuck together. They were very quiet. … They were babies.”

The schools chancellor, Joel Klein, met with teachers at P.S. 73 and deployed more than a dozen crisis counselors to help students and faculty cope with the loss. The burned-out windows at the back of the building are visible from the front of the school, which is just a block away.

“It just seems more painful and more unfair when children die,” Mr. Bloomberg said at a morning news briefing. “When children die, everyone around them seems to die a little as well.”