By DON THOMPSON, Associated Press

SACRAMENTO, Calif. (AP) — Four inmates remained hospitalized with gunshot wounds Thursday, a day after California correctional officers opened fire to quell a rare mass attack on eight prison guards by more than 100 inmates, officials said.

One Pelican Bay State Prison inmate will need surgery after he was shot in the chin. The other three were shot in the arms and legs, Corrections Department spokeswoman Terry Thornton said.

Three more inmates were sent back to prison after being treated for injuries to their back, head or foot.

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

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

“They all suffered numerous facial injuries,” Thornton said of the correctional officers. She described them as having “beating-type injuries. It doesn’t appear that a weapon was used even though (investigators) recovered two weapons.” Both appeared to be makeshift weapons that inmates grabbed during the assault, she said.

Guards fired 19 rifle bullets and three hard foam rounds to stop the attack, which began as one sergeant and seven officers were trying to break up a fistfight between two inmates in an exercise yard holding about 300 prisoners.

They were among about 2,000 inmates in the maximum-security prison near the Oregon border.

Of those inmates in the exercise yard, 107 have been isolated in a disciplinary housing unit because they are believed to have participated in the assault, Thornton said. That’s up from the initial 97 inmates sent to the disciplinary unit immediately after the attack.

Investigators aren’t sure what sparked the inmates to swarm the officers, or if it was premeditated or spontaneous. They also don’t yet know if it related to prison gangs or to racial tensions, she said.

Officials also are waiting until the investigation is completed before they decide if they need to change their procedures or responses to the unusual mob attack on prison guards, she said.

Large-scale fights among inmates are not uncommon, but frequently leave employees untouched.

The California attack came the same day as four inmates were injured at a privately operated Arizona prison during a brawl involving about 80 prisoners. Officials there said the fight at the Red Rock Correctional Center, located in the small city of Eloy, was racially motivated.

[Featured Image: AP Photo/Rich Pedroncelli, File]