BLYTHE, Calif. — Eight corrections officers and an incarcerated man were injured in a riot involving around 200 inmates in the recreational yard of a Southern California prison, authorities said Thursday.

The violence erupted around 10 a.m. Wednesday as officers were escorting an inmate across the yard as part of a contraband investigation at Ironwood State Prison in Blythe, according to the California Department of Corrections and Rehabilitation.

The inmate headbutted a staff member, and as he was being subdued, “approximately 200 incarcerated people on the yard rushed toward the officers attacking them with fists and rocks,” the department said in a statement.

After shooting a rifle warning round, officers used “chemical agents and non-lethal impact rounds” to get the melee under control, the statement said.

Eight staff members and one inmate were treated at an outside hospital and later returned to the prison, officials said. The extent of their injuries wasn't available.

So far, 30 inmates have been identified as having direct involvement in the riot, and the investigation is ongoing.

Movement was restricted in yards and dayrooms at all prisons statewide for 24 hours as officials conducted a routine threat assessment.

Ironwood, a minimum-medium security facility in the desert east of Los Angeles, opened in 1994 and houses about 2,500 male inmates.

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