A disturbance at an Oklahoma prison that left three inmates dead and five injured follows a large brawl earlier this summer in which several prisoners at the facility were hurt.

Steve Owen, a spokesman for a private company that owns and operates the Cimarron Correctional Facility in Cushing, said Saturday's disturbance lasted about 40 minutes and was contained to one housing pod.

No staff members were injured in the incident, which he said staff quelled around 4:40 p.m.

The inmates who were hurt were taken to hospitals. It's not clear what caused their injuries.

The names of those killed and injured were not immediately released.

Owen of the Nashville, Tennessee-based Corrections Corporation of America said the prison was placed on lockdown and inmates confined to their housing areas. The facility about 50 miles southwest of Tulsa in northeast Oklahoma houses medium- and maximum-security male inmates for the Oklahoma Department of Corrections.

Department of Corrections spokeswoman Terri Watkins said the incident occurred in a medium-security portion of the prison. The Cimarron Correctional Facility houses about 1,600 inmates, she said.

In June, between 200 and 300 inmates were involved in a brawl at the prison. Eleven prisoners were taken to hospitals after the fight and the facility was placed on lockdown. The fighting occurred among inmates in three separate housing units. No correctional workers were injured.

Owen said incident Saturday remains under investigation.