Willis was apparently taking the afternoon off from the shooting but rushed to the set after receiving a phone call about the accident.
The five-storey building set, where they had planned to shoot for the next five days, went up in flames during a shooting accident, the Daily Mail reported.
Willis' stunt double was working on a scene, which involved fire to break down in the building's lobby as a helicopter lands but the scene went wrong as the copter fanned the fire and caused flames to spread.
The stunt double narrowly escaped injury and fire brigades from the surrounding areas appeared on the scene to try to contain the blaze.
The 57-year-old arrived just moments after the blaze started and attempted to help salvage equipment and cameras that were in danger of being destroyed.
The actor reprises his famous John McClane character in the film.
