At least 19 people died, including nine children, and 63 were injured as a massive fire ripped through a high-rise residential apartment building in New York City on Sunday.

The blaze was caused by a portable electric heater, fire department officials said.

"We know that we have 19 people who are confirmed dead, as well as several others in critical condition among the 63 who were injured," New York Mayor Eric Adams told CNN.

"This is going to be one of the worst fires in our history," he said.

"The marshals have determined through physical evidence and through first-hand accounts by the residents that this fire started in a bedroom in a portable electric heater," New York City Fire Department Commissioner Daniel Nigro told journalists.

At least 200 firefighters responded to the blaze, which broke out just before 11:00 am on the second and third floors of a 19-storey building on East 181st Street, several blocks west of the Bronx Zoo.

The injured were taken to five hospitals; many suffered from cardiac and respiratory arrest and severe smoke inhalation, officials said.

Daniel Nigro said that flames quickly engulfed much of the structure and that the smoke was so dense as to be "unprecedented."

"Members found victims on every floor, in stairwells," Nigro told reporters.

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He explained that the fire originated in a duplex apartment on the second and third floors of the building. Since the door to the apartment had been left open this allowed the fire and smoke to spread, Nigro said.

"If you close the door the smoke and fire spread is contained within that apartment instead of spreading up the stairs," he told reporters.

He said that the building did not have any fire escapes.

"The last time we had a loss of life that may be this horrific was a fire which was over 30 years ago, also here in the Bronx," he added.

Photographs and video posted on social media showed flames and thick black smoke billowing out of a third-storey window of the building as firefighters fought the flames.