The identities of those who died have still not been released, but authorities said the children who died were a 4-year-old girl, two 5-year-old girls, a 6-year-old boy, two 11-year-old girls, a 12-year-old boy, and one additional child whose age hasn't been confirmed.
Ten children remain hospitalized in various conditions.
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FDNY Commissioner Daniel Nigro said the deceased were taken to seven different hospitals, and he explained a revision from 19 to 17 fatalities as the result of a double count in two cases.
However, he said there remain critically injured victims and he braced the community for a possible increase in the death toll.
About 200 firefighters battled the five-alarm blaze that started on the third floor of the 19-story Twin Parks North West apartment building, located at 333 East 181st Street in the Tremont section, just before 11 a.m. Sunday.
At least 44 people were injured, with 13 said to be "clinging to their lives" in nearby hospitals. Several are intubated.
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Nigro said the FDNY is certain the cause was a malfunctioning electric space heater that set a mattress on fire.
While the fire was contained to the duplex where it started on the second and third floors and the adjacent hallway, the smoke traveled throughout the building. It was the smoke that caused the fatalities.
Mayor Eric Adams said his takeaway from the fire is "close the door," and that the city would be reminding New Yorkers of that message.
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The door to the fire apartment and one on the 15th floor did not shut automatically as they should have, allowing smoke to escape and billow throughout the building.
Mamadou Wague told Eyewitness News reporter Josh Einiger that fire started in his third floor duplex, where he lives with his wife and eight kids, one of whom was trapped on a burning bed.
Wague has burns on his nose from when he leapt through the flames to rescue his daughter, who is burned but alive.
"We were sleeping and my kids were screaming, saying 'Fire, Fire!'" he said. "So I see the fire in the mattress, and I told everybody, 'Get out, get out.'"
Smoke alarms were operable, but the open door allowed heavy smoke to spew out through the building and into the stairwells as residents tried to escape.
"They are self closing but the door on 15 and the door to the fire apartment were not functioning as they should," Nigro said. "The door was not obstructed. The door when fully opened stayed fully opened because it malfunctioned."
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A city official says the building's owners told them all the doors are self closing and that building workers confirmed the self closing mechanism was operational on the fire apartment door when the lock was repaired last July,
Investigators tested the self closing mechanisms on all doors in the building Sunday and most worked, though the door on the fire apartment did not, as well as a couple others.
Firefighters described a hellish scene.
"It was absolutely horrific," Firefighters Association President Andrew Ansbro said. "I talked to many veteran firefighters who said it was the worst fire they had seen in their lives. They were doing CPR on people outside. It was absolutely horrific. Members operated with upmost heroism. Unfortunately, not all fires have a positive outcome. It's horrible. This fire will be with these members forever."
The patients are spread out among hospitals like Jacobi Medical Center, Westchester Medical Center and New York Presbyterian Hospital/Cornell.
"My heart is with the loved ones of all those we've tragically lost, all of those impacted, and with our heroic FDNY firefighters," Governor Kathy Hochul said. "The entire state of New York stands with New York City."
Tysenn Jacobs returned to her home Monday, hoping to retrieve medication.
"I dropped on my knees and started to pray to God, 'God, please help us.' It was too much," she said. "I lived in this building over 30 years. I've never seen anything like this."
Meanwhile, neighbors are rushing to help.
"My kids and I agreed to donate jackets, baby clothes, cereal, whatever we had at home that we could spare, I'm giving away now," area resident Johnanna Bellevue said. "We live here. We're a community, so one hand washes the other."
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The building was emptied of residents Sunday night, but some residents were able to return to Twin Parks North West Monday night to both retrieve items and move back in if they choose to do so.
However, this does not apply to the floor where the fire started as the DOB has not yet lifted their Partial Vacate Order which applies to the third floor of the building.
Some of the returning residents carried the supplies they'd amassed over the past two days, checked in with police and went back to their homes ... or what's left of them.
"Yeah, but it's still glass everywhere, windows are broken it's freezing in there, don't wanna be in there," survivor Jovane Green said.
But there's an even bigger reason why Green won't be spending the night.
"You hear the screaming the people that was ready to jump, everything. It's all I see," Green said.
Monday night might have been too soon for him to go back home. But he may never be ready.
"I'm gonna think about it every time I walk in there. You're just gonna remember everything that happened, all the lives that was lost. Every time I walk in there," Green said.
Many of the victims are Muslim immigrants from the West African nation of Gambia, and Mayor Adams urged all to seek help and assured their information would not be passed on to federal immigration authorities.
"We just want, right now, to give the families the support they deserve," he said. "And let the marshals do their job to determine what happened here."
He praised the firefighters who responded to the scene, calling them heroes.
"Many of them, their oxygen tanks were on empty," he said. "But instead of turning back and exiting the building, they pushed through, through the smoke."
It is New York City's deadliest blaze in three decades.
The Consumer Product Safety Commission (CPSC) estimates that portable electric heaters are involved in about 1,100 fires per year, while the National Fire Protection Association claims space heaters were most often responsible for the home heating equipment fires, accounting for more than two in five fires, as well as the vast majority of deaths (81%) and injuries (80%) in home fires caused by heating equipment.
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