NEW YORK (AP) — The New York Fire Department says a boiler venting heat sparked the blaze that killed a firefighter in a Harlem building being used as a film set in March.

FDNY marshals said Tuesday that the heat from the boiler ignited nearby combustible materials in the cellar of the building, and the building's sprinkler system had been shut off. Thirty-seven-year-old Michael Davidson was killed in the March 23 fire.

At the time, the building was being used to film Edward Norton and Bruce Willis' upcoming film "Motherless Brooklyn."

Davidson's death is also under investigation by the FDNY's Safety Command.