A malfunctioning electric space heater in a bedroom was the source of an apartment building fire in the Bronx that killed 17 people, including 8 children, making it one of the worst fires in the city's history, New York Mayor Eric Adams said.
Mayor Adams revised the death toll on Monday down from 19, saying it was an evolving situation.
A CNN review of local hospitals shows that at least eight patients are still hospitalised in relation to the fire, while at least 25 people have been treated and released.
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Now, the building's fire alarms and a series of open doors are on the radar of investigators and officials probing the second major deadly fire in a week in the Northeast.
The Bronx blaze was deemed the second most deadly US home fire in nearly 40 years by the National Fire Protection Association.
The NFPA also reported that heating equipment is the second-leading cause of US home fires and the third-leading cause of home fire deaths and injuries.
"This is a horrific, horrific, painful moment for the city of New York, and the impact of this fire is going to really bring a level of just pain and despair in our city," Mayor Adams said on Sunday.
Many of those in the building were Muslim immigrants from the West African nation of The Gambia.
The country's ambassador told CNN the building had been a beloved home for many such immigrants over the years.
"I think a lot of Gambians who came here, they stayed there before they moved anywhere else. This was kind of a first port of call, this building. It's a building Gambians have a lot of attachment to," said Ambassador Dawda Docka Fadera, who travelled from Washington to New York after learning of the fire.
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The families in the apartment complex and neighbourhood told CNN they were devastated.
Some are still searching for loved ones, and all are desperate for answers.
"I'm totally worried and devastated — not me alone, but the whole community and the family at large. Everybody's worried. We don't know what happened. That's the toughest thing — not knowing," says Yusupha Jawara, who spoke with CNN at a mosque where many were praying for the victims.
The Red Cross has provided emergency housing to 22 families, representing 56 adults and 25 children, the group said in a statement.
The five-alarm fire began shortly before 11am local time and first consumed the bedroom, then the entire duplex apartment on the second and third floors of the 19-story building, Commissioner of the New York City Fire Department (FDNY) Daniel Nigro said.
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"The heat was on in the building. This (the space heater) was being used to supplement the building heat. There were smoke alarms throughout the building. The first call that came in was due to a neighbour hearing the smoke alarm and looking and seeing the smoke and calling," he said.
When residents left the fiery unit, the apartment door was left open, allowing the blaze to spread, Mr Nigro said.
The fire was contained to that hallway, but the smoke travelled upwards and took over much of the building.
The doors were supposed to close automatically, but the apartment door as well as the door from the stairwell to the 15th floor were not functioning properly, Mr Nigro said.
"The smoke spread throughout the building, thus, the tremendous loss of life and other people fighting for their lives right now in hospitals all over the Bronx," he said.
"So, we are investigating where everyone was found, how the smoke travelled, but certainly the marshals have determined through physical evidence and through first-hand accounts by the residents that this fire started in the bedroom, in a portable electric heater."
About 200 members of the FDNY responded to the fire at 333 East 181st Street, the agency said.
Units arrived at the scene within three minutes of getting an emergency call, Mr Nigro said. They "found victims on every floor in stairways," he said, many of them in cardiac and respiratory arrest.
"It was a very difficult job for our members. Their air tanks contained a certain amount of air — they ran out of air, many of our members — and they continued working to try to get as many people out as they could," he said.
Residents say they narrowly escaped smoke and flames
Daisy Mitchell, a 10th-floor resident who had just moved into the building, was one of those who fled to safety.
She told CNN's Brianna Keilar her husband first smelled smoke and noticed the fire.
"The alarm was going off for a while so I didn't pay it no mind," she said.
"Then, when he opened the door and I went out there, I passed out — it was devastating, it was like really scary.
"I went to the stairs, I opened the door, it just blew me back [to] the house," she added.
"If I'd stayed out there for another three seconds, I would have been gone too."
It was common for fire alarms to go off in the building, 10th-floor resident Chanasia Hunter told CNN affiliate WABC.
"So, when you don't know that it's a fire, like, you know, how would you supposed to know if it's a fire or if it's always going off?" said Ms Hunter, adding she got a call from a resident on the third floor warning her of the fire, then a knock on her door telling her and her family to get out.
Karen Dejesus lives on the same floor as the apartment that caught fire and said the flames encroached on her residence.
"I can see the flames, I can see the smoke and everything, you know, coming into my apartment," Ms Dejesus said.
"You're being trapped somewhere. As you see, we have no fire escapes, obviously the building was not fireproof like we thought it was."
Ms Dejesus said firefighters broke down her door to rescue her, her granddaughter and her son.
They had to climb out of a window to escape the flames.
She, too, noted fire alarms in the building often went off.
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"So many of us were used to hearing that fire alarm go off so it was like second nature to us," she said.
"Not until I actually seen the smoke coming in the door, I realised it was a real fire and I heard people yelling help, help, help."
"I thank God that me and my family are safe," said Ms Dejesus.
"I'm sorry for all of my neighbours that didn't make it, I'm sorry for my neighbours that are still in the hospital fighting for their life. This was crazy, this was so scary."
Fire alarms and self-closing doors focus of investigation
Investigators are examining potential issues with the fire alarms and with self-closing doors designed to contain fire and smoke.
Reports of smoke alarms frequently malfunctioning will be looked into, Mr Nigro said, adding he couldn't confirm them.
The building had no fire escapes, but "there are interior stairways," he said.
"So, the residents should know where the stairwells are, and I think some of them could not escape because of the volume of smoke."
Mayor Adams, speaking to CNN's Brianna Keilar, said fire marshals will investigate the self-closing doors in the building to see if there was a malfunction.
New York passed a law in 2018 making self-closing doors a requirement in buildings with three or more apartments.
"We have a law here in NYC that requires doors to close automatically," he said.
"We also want to double down on that PSA that I recall as a child... close the doors," he said.
There have been no major building violations or complaints listed against the building, which contains 120 units, according to city building records.
Past minor violations were rectified by the property, and no structural violations were listed.
Built in 1972, the building was federally funded, so may have been built outside the New York City fire code, Mr Nigro said, adding it was unlikely to have been a factor in Sunday's blaze.
"Certain federal buildings can be built under different standards. But to be perfectly clear, the fire itself — other than getting in the hall because the door was open — never extended anywhere else in the building, so that was not a factor."
At a news conference on Monday, New York firefighter union representatives confirmed the building was not required to adhere to city fire codes.
"There was different fire protection in this building than we have in tenements and other high rises under the New York City code," said Jim McCarthy, president of the FDNY Fire Officers Association.
"So it exposed members to a more dangerous atmosphere."
Life-saving fire protection devices like sprinkler systems were oftentimes not a requirement in older buildings, Mr McCarthy said.
Many older buildings in the city have been retrofitted with sprinklers, McCarthy said. It doesn't appear this building had a sprinkler system installed, according to Andrew Ansbro, president of the Uniformed Firefighters Association.
For the victims, the city will work to ensure Islamic funeral and burial rites are respected and will seek Muslim leaders to connect with residents, said Mayor Adams, who took office only this month.
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The names of those who request government assistance will not be turned over to Immigration and Customs Enforcement, he added.
Residents of the apartment building were initially housed at a middle school next door, and longer-term shelter for them would be found, said Christina Farrell, first deputy commissioner of NYC emergency management.
Low-income areas face higher fire risk, official says
The "tragic and terrifying" fire underscores the need for federal investment in affordable housing, said Congressman Ritchie Torres, who represents residents of the apartment building.
"Many of these buildings are old. Not every apartment has a fire alarm. Most of these buildings have no sprinkler system. And so the risk of a fire is much higher in lower-income neighbourhoods in the Bronx than it might be elsewhere in the city or in the country," Mr Torres told MSNBC.
"When we allow our affordable housing developments to be plagued by decades of disinvestment, we are putting lives at risk. These buildings are wide open to catastrophic fires that can cost people their lives, including the lives of children."
The Bronx has been the scene of other grave fires in recent decades — the most deadly in 1990, when 87 people died at the Happy Land social club.
In 2007, 10 people — nine of them children — were killed in a fire at a residence after a space heater cord overheated.
In December 2017, 13 people died when a fire broke out at an apartment block.
The fatal fire began when a three-year-old played with burners on the stove and started a kitchen fire, officials said.
When the boy's mother fled the apartment with him and his two-year-old sister, she left the door open.
The apartment's stairway acted "like a chimney," and the fire rapidly spread through the apartment building, Mr Nigro said at the time.
After that fire, the city passed the self-closing door law.
