Producers canceled a Wednesday matinee performance of "Spider-Man: Turn Off the Dark" after Monday evening's 30-foot plunge of a Spider-Man stunt double into a stage pit. State investigators weren't sure whether the equipment, the rigging or the performer caused the fourth accident in the troubled show.

Actors' Equity Association called it human error, but Leo Rosales, a spokesman for the state Department of Labor, said the cause was under investigation. Rosales said the show's producers would present the new safety protocols on Wednesday. If the measures are inadequate, he said, the state will not let the show perform the complicated aerial maneuvers.

"If it takes longer, it will need to take longer," he said of the show's timing. "We need to be satisfied."

The musical, which started previews a month ago without benefit of an out-of-town tryout, could be put in jeopardy if certain aerial actions aren't allowed; it would lose some of its razzle-dazzle. Monday's performance of "Spider-Man: Turn Off the Dark," the most expensive production in Broadway history, ended just minutes before its curtain when Christopher W. Tierney, a stuntman playing the superhero, fell into the stage pit. The safety tether that clips to his back failed to prevent the spill.