Two staff members at Tecumseh State Correctional Institution were assaulted this morning when a group of inmates refused to return to their cells.
One of the staff members was seriously hurt but it's not believed to be life threatening.
The inmates in one housing unit were refusing to return to their cells, but later did so without the need for force.
The prison is in modified operations and will remain so during an investigation into the incident. No weapons were used and no damage to the facility is reported.
All visits have been cancelled for today.