Fourteen Michigan Department of Corrections officers in the western Upper Peninsula required medical attention following a brief melee with prisoners Sunday night, a department spokesman said Monday.

Officials are investigating the possibility that a protest by a group of black inmates that immediately preceded the melee stemmed from a fight between two inmates – one white and one black – that occurred earlier in the day, spokesman Russ Marlan said.

Only one of the injured officers remained hospitalized Monday, he said. According to prison officials, here's what happened:

The officers were attacked about 8:45 p.m. Sunday after a group of 35 prisoners at the Ojibway Correctional Facility near Marenisco had emerged from a dayroom. Marlan said they had gone into the room and refused orders to leave “in some kind of protest.”

Although the prison had activated emergency response procedures when the protest occurred, it appeared to have been defused when the inmates had exited the dayroom and were expected to move into their cells. But about 15 of the inmates suddenly set upon the officers, striking blows with their fists.

The cellblock officers, aided by a team of emergency response officers, quickly restored order and the prisoners were returned to their cells.

Marlan said no weapons appeared to have been used by the prisoners and injuries were largely limited to cuts and bruises. The 15 prisoners believed to have been involved have been transferred to more secure facilities, he said.

Marlan said he had no additional information about the earlier fight between the inmates or the nature of the black inmates' grievance. An investigation is underway, he said.