Corrections officials say the riot began with a fight between two Los Angeles County street gangs, one black and one Hispanic. Other inmates joined in the fracas.
Corrections Department spokeswoman Terry Thornton said the gangs were continuing a dispute that began with a smaller fight in May.
Officials plan to ask the San Bernardino County District Attorney's Office to file criminal charges, including attempted murder and battery, against 25 inmates who took part in the melee.
Officials have already charged 222 inmates with rules violations that could lengthen their sentences.
The Associated Press contributed to this story.