Orange County fire investigators were at the scene Saturday trying to determine why the stage at the Servite High School gave way during a performance, the Los Angeles Times reported Sunday.
"Early investigations suggest the front of the stage gave out due to weight," Anaheim police spokesman Lt. Tim Schmidt said.
About 250 girls from Servite's sister Catholic school, Rosary High School, were on the stage when it collapsed, Schmidt said.
Schmidt said about 24 students suffered "minor to moderate" injuries.
Three-hundred to 400 students and parents were in the auditorium at the time of the collapse, police said.
The students were performing in "Red and Gold," Rosary High's annual musical theater challenge, the Times said. Servite High School is an all-boys Catholic School in Anaheim. Rosary is an all-girls sister school in Fullerton.