New York City Fire Department officials say fire marshals determined that unapproved electrical wiring caused a huge fire in the East Village last week.
It happened on the roof of a building, which houses apartments and a laundromat, on East Houston Street near Avenue A.
More than 180 firefighters responded to the scene and eight suffered minor injuries.
Teams used tower ladders and stretched hoses from the roof of an adjacent building to put out the flames.
Officials have said there was work being done when the fire started.
Meanwhile, fire marshals say a fire in Greenwich Village Monday was caused by somebody smoking.
The fire broke out on the roof of a building housing an Urban Outfitters at 628 Broadway between Houston and Bleecker Streets.
Officials said three people, including one firefighter, received minor injuries.
A fire chief said the summer heat was a contributing factor.