Steve Owen, a spokesman at the facility, said staff quelled the violence at around 4:40pm local time yesterday.

Additionally, no prison staffers were injured during the incident, according to FOX 23. It’s not clear what caused their injuries.

The names of the deceased have not yet been released, pending notification of their family members.

Cimarron Correctional Facility has been placed on lockdown after the riot, which lasted for about 40 minutes, local media said.

The facility, about 50 miles southwest of Tulsa, houses both medium and maximum-security male inmates for the Oklahoma Department of Corrections.

Corrections Corporation of America, one of nation’s largest private prison companies, contracts with various states and other entities to house inmates.

Division of Corrections spokeswoman Terri Watkins stated the incident occurred in a medium-security portion of the jail.

Cimarron is owned and operated by Corrections Corporation of America.

According to NBC News, between 200 and 300 inmates were involved in the altercation.

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. Sometimes, weapons are smuggled in from the outside, but with increasing security, this is more hard to accomplish.

Three inmates died in an incident at the Cimarron Correctional Facility. In the words of the court, the state’s prisons were “bursting at the seams”, with conditions so dire that “a California inmate was dying needlessly every six or seven days”.