UPDATED | December 29, 2017  10:15 AM

NEW YORK (AP)New York City’s deadliest residential fire in decades was accidentally lit by a 3 ½-year-old boy playing with the burners on his mother’s stove, officials said Friday.

The flames spread quickly through the kitchen, then roared through a door the boy’s mother had left open as she fled her first floor apartment with her two children, Fire Commissioner Daniel Nigro said. A stairwell acted like a chimney, carrying the flames through the entire building within minutes and blocking the main escape route.

Twelve people died, including girls ages 1, 2 and 7 and a boy whose age was not given.

“We were told the boy had a history of playing with the burners and turning them on, and before the mother knew it, this fire had gotten a good hold of the kitchen,” Nigro said.

Many residents of the building were able to flee via fire escapes. At least 20 people were clambering down the icy, metal escapes when firefighters arrived, Nigro said.

Excluding the Sept. 11 attacks, it was the deadliest fire in the city since 87 people were killed at a social club fire in the same Bronx neighborhood in 1990.

The blaze broke out on the first floor of a five-story building just before 7 p.m. and quickly tore through the roughly century-old structure near the Bronx Zoo.

Some tenants of the building, a mix of native New Yorkers and Latino and African immigrants, climbed down fire escapes. But the flames moved so fast that many never made it out of their apartments.

The cause of the fire remained under investigation.

About 170 firefighters worked in bone-chilling cold, just 15 degrees, to rescue about a dozen people from the building.

Thierno Diallo, 59, a security guard originally from Conakry, Guinea, who lives in a ground floor apartment said he was asleep when he heard banging on the door. It took him a moment to realize what was happening.

“Only when I heard people screaming, ‘There’s a fire in the building!'” he said. “I heard somebody, ‘Oh! Fire! Fire! Fire!'”

He ran outside in his bathrobe, jacket and sandals.

Kenneth Kodua, 37, said he left his apartment to get food, leaving his roommate behind, and came back to find people fleeing in a panic.

Hours later, he was still trying to find out whether his roommate had escaped.

“I tried calling her. I tried calling. No answer,” he said, still clutching his bag of uneaten food. His phone was dead.

Many questions remained in the immediate aftermath of the blaze, including how the fire spread so quickly in a brick building built after catastrophic fires at the turn of the 20th century ushered in an era of tougher enforcement of fire codes.

The building had more than 20 units. It was not new enough that it was required to have modern-day fireproofing, like sprinkler systems and interior steel construction.

Witnesses described seeing burned bodies being carried away on stretchers and young girls who had escaped standing barefoot outside with no coats.

Twum Bredu, 61, arrived in the neighborhood looking for his brother, who had been staying with a family in the building. The family, a husband and wife and four children, got out. But there was no word about his brother.

“I’ve been calling his phone, it’s ringing, but nobody picks up,” Bredu said. “He was in his room, and we don’t know what happened.”

The death toll surpassed the 10 who died, including nine children, in a four-story home in another part of the Bronx in 2007. That blaze had been sparked by a space heater.

(© Copyright 2017 The Associated Press. All Rights Reserved. This material may not be published, broadcast, rewritten or redistributed.)

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