LINCOLN, Neb. (AP) — Prisons officials say staff members at the Nebraska State Penitentiary have regained control of a group of inmates who refused orders to return to their living quarters. A statement from the Nebraska Department of Correctional Services says the prison is on lockdown status after the incident Tuesday evening.

According to the statement, a group of inmates who had been ordered to return to their housing unit from the dining hall refused to leave a yard. A group of inmates “converged on staff” and inmates throughout the facility “became defiant” and “verbally aggressive.”

A warning shot was fired from a guard tower in an effort to bring the detainees in line. Warden Rich Cruickshank says staff regained control and secured the facility. The statement says no staff or inmates were injured.

The facility will be on lockdown status while the incident is investigated.