(CNN) -- Guards fired rounds to quell a "major riot" in the main yard of a prison in central California on Friday, a corrections department spokesman said.
It was not clear what triggered the riot at Folsom State Prison. It began around 7:30 p.m. (10:30 p.m. ET).
Five inmates were injured and three were taken to nearby hospitals, said spokesman Luis Patino of California Department of Corrections and Rehabilitation.
There were no fatalities, he said. No corrections officers were injured.
Folsom State Prison is about 20 miles from Sacramento. It is the second-oldest state prison, and houses medium-security inmates, according to the department of corrections.
Music legend Johnny Cash performed for inmates and recorded an album there in 1968.