A correctional officer at Stearns County Jail was assaulted by an inmate on Thursday evening.
The incident happened at the end of the evening meal while officers were trying to locak the inmates down.
One of them, a 26-year-old man, refused to lock down.
While officers tried to return the inmate to his cell, the inmate punched one of them in the face with a closed fist.
Several more officers came over and secured him in his cell.
The correctional officer was taken to St. Cloud Hospital, where he was treated and released having suffered non-life-threatening injuries.
The inmate is under investigation and is facing criminal charges.
It's the second assault on a correctional officer in the space of a week in Minnesota, with an officer having been seriously injured by an inmate a Sherburne County Jail on Monday.