A statewide warning was issued to every California prison after roughly 200 prisoners were involved in an attack on officers at Ironwood State Prison in Blythe on Wednesday, officials said.
Eight staff members and one prisoner were briefly hospitalized and treated for undisclosed injuries in the incident, prompting the California Department of Corrections and Rehabilitation to conduct a threat assessment at all its prisons.
The incident occurred Wednesday morning while members of CDCR's Investigative Services Unit were escorting a prisoner across the prison yard as part of a contraband investigation.
In a statement, CDCR officials said the prisoner, who was not identified, headbutted a staff member.
"He was immediately subdued," the statement read. "At the same time, approximately 200 incarcerated people in the yard rushed toward the officers."
Prisoners were using fists and rocks, and they refused multiple orders to stop, officials said.
One staff member fired a warning shot from a rifle, officials said, and guards used chemical agents and non-lethal impact rounds during the incident.
Located about 20 miles away from the California-Arizona border, Ironwood State Prison houses more than 2,500 prisoners, the CDCR reports.
According to the CDCR, the 640-acre facility houses inmates who are about four years from being released.
After the riot, officials alerted the rest of the state's 33 adult facilities about the incident and issued a "modified programming."
A spokesperson for the CDCR said the agency did not issue a "lockdown." Instead, some programs and prisoner movement was limited, but not all activities were suspended.
The restriction was lifted for the other prisons Thursday, a spokesperson said. One of Ironwood's sections, Facility D, remains under modified programming while the incident is being investigated. But normal activities have resumed at the rest of Ironwood.
At least 30 people were identified as having directly participated in the riot, officials said.
This story originally appeared in Los Angeles Times.