Seven inmates were injured Sunday when a fight broke out at the North Fork Correctional Center in Sayre. A spokeswoman says the fight took place in the prison's housing unit. Four inmates were taken to hospitals in Sayre and Elk City for treatment. None of the injuries was life-threatening. The prison is currently on lockdown and visitation has been cancelled at least through Thursday. North Fork is a medium-security prison for men, with about 2,200 inmates. It is operated by the Oklahoma Department of Corrections.