About 100 firefighters and a dozen fire engines were required to extinguish the blaze after a technician accidentally ignited the fireworks, the BBC reported.
The blast occurred at the 4,500-seat Palais des Sports before the play, "1789, The Lovers of the Bastille," had begun. All of those injured were either cast members or stagehands.
A power tool being used too close to the pyrotechnics may have caused the explosion, the report said.
A production worker suffered a heart attack and died after the blast, Radio France Internationale reported.
Four other people were seriously injured and 10 received minor injuries.
The explosion collapsed a wall and part of the ceiling at the arena. The shock wave from the blast was felt in nearby buildings.
The play's weekend performances were canceled.