FORDHAM HEIGHTS, the Bronx — A Bronx fire that left 17 dead, including eight children, was likely caused by a space heater, Mayor Eric Adams said Sunday.

The mayor later announced the revised death toll on Monday afternoon.

The malfunctioning electric space heater was in an apartment bedroom, FDNY Commissioner Daniel Nigro said. Heat was on in the building; the portable device was used for supplementary warmth.

The door to the apartment where the flames broke out was left open.

“The door to that apartment was left open, causing the fire to spread and the smoke to spread,” Nigro said. “This fire took its toll on our city.”

There were smoke alarms throughout the building, Nigro said.

But one resident said the building regularly had false alarms.

Building resident Luis Rosa said he was awakened Sunday by a fire alarm, but dismissed it at first, thinking it was one of the building’s periodic false alarms.

But when a notification popped up on his phone, he and his mother began to worry. By then, smoke began wafting into his 13th-floor apartment and he heard sirens in the distance.

He opened the front door, but the smoke had gotten too thick for an escape, he said.

“Once I opened the door, I couldn’t even see that far down the hallway,” Rosa told The Associated Press. “So I said, OK, we can’t run down the stairs because if we run down the stairs, we’re going to end up suffocating.”

“All we could do was wait,” he said.

Editor’s note: Mayor Eric Adams announced a revised, slightly lower death toll on Monday afternoon.