SAN LUIS OBISPO, Calif. (AP) — California officials say a fight involving about 40 inmates has left four injured at a state prison 200 miles northwest of Los Angeles.

Officials say about 20 medium-security inmates rushed a group of about 10 inmates Wednesday afternoon at the California Men’s Colony State Prison in San Luis Obispo. Another 10 inmates soon joined the fight in an exercise yard.

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Guards used pepper spray and non-lethal projectiles to stop the fighting.

Four inmates had slashing or stabbing wounds, and two were taken to a hospital for treatment of non-life threatening injuries.

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At least one inmate-made weapon was recovered.

No employees were hurt.

Inmate movement in the housing unit has been restricted while officials investigate the cause of the fight.

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The prison houses about 3,800 minimum- and medium-custody inmates.