PARIS — A theater technical director died of a heart attack after a malfunctioning power tool set off an explosion at the venue, investigators said Saturday.

An initial investigation determined that a first blast, which occurred near the stage shortly after 6 p.m. Friday, was caused when the disc of a circular power saw broke away and ignited fireworks stored nearby.

Marcus Toledano, 41, was among several people who rushed to the scene, and a second explosion ensued, causing a wall to collapse. Several others were injured, five seriously, police said.