Space heater blamed after 19 die in one of the worst fires in modern New York history - CNN

Nine children were killed, while 63 people were injured by "severe smoke inhalation," with 32 sent to five borough hospitals in life-threatening condition, Fire Commissioner Daniel Nigro said Sunday in a news conference.

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.

"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," said Mayor Eric Adams.

The first call that came in was due to a neighbor 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 smoke and fire to spread, Nigro said.

"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 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.

Reports of smoke alarms frequently malfunctioning will be looked into, 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.

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, Nigro said, adding it was unlikely to have been a factor in Sunday's blaze.

When the boy's mother fled the apartment with him and his 2-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, Nigro said at the time.