SPRINGFIELD, S.D. (AP) — South Dakota corrections officials say they are investigating a pair of incidents at the state prison in Springfield that left six inmates injured.

Department of Corrections spokesman Michael Winder said in a statement that fighting began Tuesday night at the Mike Durfee State Prison, followed by another incident Wednesday morning. The six inmates suffered non-life-threatening injuries, he said.

Winder also said some prison staff suffered minor injuries while restoring order, but there were no assaults on personnel or damage to property. He said any evidence of criminal activity would be forwarded to the Division of Criminal Investigation.

Shouting through fencing and open windows, inmates at the converted college campus on Wednesday expressed their frustrations to reporters from the Sioux Falls Argus Leader and KELO-TV. They said they had been locked down and weren’t allowed to make phone calls to their families since the fighting broke out. Their complaints included gang activity, understaffing and the lack of air conditioning in their cells.

In March, at least one correctional officer was injured in a disturbance at the State Penitentiary in Sioux Falls, resulting in felony charges against 11 inmates.