New York City Mayor Eric Adams, just over a week into the job, said at a briefing that the city's medical examiner determined the fire had claimed two fewer victims than the 19 announced on Sunday.

The blaze broke out on Sunday morning in the 19-floor Twin Parks North West building, which provided affordable housing units for low-income New Yorkers. Many of the residents were from the large Gambian community that lived in the neighbourhood.

"This is a global tragedy as The Bronx and New York City is representative of the ethnicities and cultures across the globe," Adams said during a briefing in front of the building on Monday. "This is an evolving crisis. An unspeakable tragedy."

Adams said he spoke with US President Joe Biden, who pledged that the White House will provide "whatever" New York City needs to address the aftermath of the fire.

It was the second major fire in a residential complex in the United States this week after 12 people, including eight children, were killed early on Wednesday when flames swept through a public housing apartment building in Philadelphia.

Earlier in the day on "Good Morning America," Adams said smoke from the fire was able to spread due to a door being open. Doors in apartment houses are required to close automatically to prevent fires from spreading through the building.

"There may have been a maintenance issue with this door and that is going to be part of the ongoing investigation," Adams said. "This is all going to come out during the investigation."

Addressing the revised death toll, Fire Commissioner Daniel Nigro said patients had been taken to seven different hospitals in the city, which led to "a bit of a double count," adding that many remain in care still fighting for their lives.

Investigators are looking into the possibility that a door from 15th floor to stairway was not functioning as it should, Nigro said, adding that residents would have been safer if they stayed in their apartments rather than exiting down stairways.

Some 60 people were injured in the blaze and 32 people had been hospitalised with life-threatening injuries, officials said on Sunday.

Fire marshals determined through physical evidence and accounts from residents the fire started in a portable electric heater in the apartment's bedroom. The heat had been on in the apartment building and the portable heater had been supplementing that heating, they said.

Some 200 firefighters helped put out the blaze.

"Many of them, of their oxygen tanks were on empty," Adams said on Monday. "But instead of turning back and exiting the building, they pushed through, through the smoke."

The building was constructed in 1972 as part of a state program to provide affordable housing.

Australian Associated Press