The incident took place in the Bronx, a fire department spokesperson said. Media reports said a gas explosion had sparked the fire and building collapse.
A video posted on the New York Post website showed flames and plumes of black smoke outside a building as police officers urged people to move away from the site.
Mayor Eric Adams was due to hold a news conference at 2:45 p.m local time (19:45 GMT).
Earlier this month 17 people died when a Bronx fire started by a malfunctioning space heater spread smoke through a low-income building. (Reporting by Kanishka Singh and Costas Pitas; Editing by Tim Ahmann and Howard Goller)