Between 200 and 300 prisoners at a private Oklahoma prison were involved in a brawl putting the facility on indefinite lockdown, state corrections officials said Thursday.

Eleven inmates were taken to hospitals Wednesday afternoon after the fight at Cimarron Correctional Facility in Cushing, state Department of Corrections spokeswoman Terri Watkins said. As of Thursday, seven remained hospitalized, but none had light threatening injuries, Watkins said. She said she did not know what kinds of injuries the inmates suffered.

The fighting occurred among inmates in three separate housing units at the facility, Watkins said. The units house a maximum of 1,650 inmates, medium- and maximum-security beds.

The prison has been placed on indefinite lockdown while officials investigate what sparked the melee, she said.

The fight lasted about 40 minutes before correctional officers were able to regain control, Steve Owen, spokesman for Nashville, Tennessee-based prison operator CCA, said.

"Public safety was never a threat," he said.

Watkins said the staff "reacted very quickly, very effectively, in containing the situation."

She said the facility, which houses only Oklahoma inmates, does not have a history of inmate violence and there was no record of recent inmate brawls.

No correctional workers were injured.

The Associated Press contributed to this report