The 17 people who were killed in an apartment fire in the Bronx died from smoke inhalation, according to ABC News, which cited the New York City Office of the Chief Medical Examiner.
Nine adults and eight children are among the dead. Investigators are still working to identify the victims.
The New York Fire Department says more than 60 people were injured in the fire. As of Monday, as many as 13 were in critical condition.
Investigators determined that a malfunctioning electric space heater started the fire in the 19-story building.
Sunday's fire in the Bronx is already the city's deadliest in three decades. It came just days after an apartment fire in Philadelphia killed 12 people, including eight children. Officials suspect that fire began when a child accidentally sparked a Christmas tree while playing with a lighter.