Deren Martinez/KTVB

Officials say a prison guard was forced to shoot his weapon in this Ontario prison after several inmates got out of control

ONTARIO - An Ontario prison is on lockdown and four prisoners are in the hospital after a guard fired a shot during an inmate fight.

Neighbors describe the scene

The shooting happened early Sunday at the Snake River Correctional Institute in Ontario, OR. 

Prison officials say about 120 inmates at the medium security prison got into a fight in the prison recreation yard Sunday morning.

A prison guard fired one shot when the violence escalated and hit one of the inmates.

A spokesperson for the prison says guards broke up the fight and paramedics transported four inmates to the hospital - one for a gunshot wound and three others for injuries from the fight.

Prison officials spent Sunday combing through evidence. They say they're not sure what started the fight, if it was a planned incident or if any guard is at fault for firing at the fighting crowd.

The Oregon State Police launched an investigation into the fight and shooting to determine what happened.

The prison remains on lockdown and all scheduled visitations have been canceled.

Prison officials have not released the names of the injured prisoners or their conditions - in fact very limited information is being released.

The Snake River Correctional Institution is a medium security prison, housing about 3,000 inmates.  It is the largest prison in the State of Oregon.