Three inmates were killed and five injured when rioting broke out on Saturday at Cimarron Correctional Facility in Cushing, Oklahoma, the New York Times reports. “The disturbance was inmate-on-inmate,” a spokesman said. “No lethal force was used by staff.”

Cimarron is owned and operated by Corrections Corporation of America. A spokesman for the private company, Steve Owen, told the Times that prison guards “quelled an inmate disturbance” just after 4:30 pm on Saturday. No prison staff were injured.

This is the second such disturbance at Cimarron in recent months. The prison was locked down for several weeks after 11 inmates were sent to the hospital following a fight in June, Oklahoma Department of Corrections spokesman Alex Gerszewski said.

“It was an altercation between inmates at that facility,” Gerszewski said. “It is currently under investigation.” According to NBC News, between 200 and 300 inmates were involved in the altercation.

According to the Associated Press, Oklahoma has the highest rate of inmate homicides in the country:

The figures reviewed by The Associated Press as part of a months-long investigation earlier this year show that there were 39 homicides at Oklahoma prisons between 2001 and 2012, a rate of 14 per 100,000 inmates. The national average is 4 per 100,000.

Cimarron is still on lockdown after Saturday’s deadly brawl, KOCO reports. Officials said that one guard, who was inside the housing pod where the fight took place, is getting counseling.

Update, 1:35 p.m. – A fourth inmate succumbed to his wounds overnight, officials said on Sunday.

Image via KOCO. Contact the author of this post: brendan.oconnor@gawker.com.