A fight on a recreation yard at Donovan State Prison Friday night turned into a riot that left several inmates injured.
The California Department of Corrections and Rehabilitation (CDCR) said a fight involving approximately 80 inmates on the recreation yard of Facility A grew into a riot at around 8:30 p.m.
When inmates refused CDCR officers' commands to stop fighting, officers used less than lethal force to try and stop them, the CDCR said.
Cal Fire said medics were sent to the prison to treat at least six patients.
An NBC 7 camera crew arrived outside the entrance to the prison at around 9:20 p.m. and saw a fire engine and several ambulances enter the facility with their sirens on. A helicopter was also seen flying over the facility.
Four inmates were taken to area hospital for injuries including puncture wounds, cuts, and head, neck and torso bruises. One inmate suffering from puncture wounds is in critical condition, the CDCR said.
Four inmate-manufactured weapons were recovered at the scene and no staff members were injured, according to the CDCR.
The incident is being investigated by the Investigative Services Unit at the prison and the Office of the Inspector General was notified.
Visiting was cancelled for Facility A, Saturday and Sunday, the CDCR said.
A riot involving nearly 50 inmates at the facility in February left 10 prisoners wounded, including one so severely that he had to be life-flighted from the prison.