California ? A California state prison near Los Angeles remained on lockdown Sunday after a riot sent 55 prisoners to hospitals and injured more than 250 inmates in all, prison officials said.

As many as 80 officers responded to the riot Saturday night, which involved some 1,300 inmates in seven dormitory-style barracks at the California Institution for Men in Chino, prison spokesman Lt. Mark Hargrove said.

The riot was likely prompted by tensions between black and Hispanic prisoners, Hargrove said.

Officers used pepper spray, wielded batons and shot foam projectiles to remove inmates who had barricaded themselves inside the medium-security facility during the four-hour uprising. A fire ignited during the chaos caused significant damage to one of the buildings, Hargrove said.

The inmates’ injuries ranged from stab wounds and slashes to head trauma, and some of the injuries were considered life-threatening, Hargrove said. No staff members were injured in the disturbance.