Updated

The Latest on a mass assault on guards at a California state prison (all times local):

3 p.m.

Four inmates remain hospitalized with gunshot wounds a day after California correctional officers opened fire to quell a mass attack on eight prison guards by more than 100 inmates.

Corrections Department spokeswoman Terry Thornton said Thursday that one Pelican Bay State Prison inmate needs surgery after he was shot in the chin. The other three were shot in the arms and legs.

All eight officers were treated and released for beating injuries, but one will need surgery for a torn shoulder. He also has a fractured eye socket.

Another officer has a broken nose, while a third needed stitches to close a wound around his left eye.

Guards fired 19 rifle bullets to stop the attack in an exercise yard holding about 300 high-security prisoners near the Oregon border.

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1:45 a.m.

Officials say a fight that forced correctional officers to open fire with real bullets to stop a melee was unusual even by the violent standard of California prisons.

Pelican Bay State Prison guards fired 19 rifle bullets to stop large groups of prisoners from attacking other correctional officers Wednesday.

Eight guards and seven inmates had to be hospitalized.

The guards had been had been breaking up a fistfight between two inmates when they were overwhelmed in an exercise yard teeming with several hundred high-security inmates.

Premeditated or not, the mass attack was unusual. Ninety-seven inmates were initially believed to have participated.

The eight guards were treated and released.

Five of the seven injured inmates were treated for gunshot wounds at the prison, which houses about 2,000 inmates near the Oregon border.