Several inmates overpowered three guards and took their keys on Friday, then freed a number of death-row inmates from their cells, prison officials said.
The death-row inmates were in a small housing unit outside their cells but still inside the Mansfield Correctional Institution, a state prison 60 miles northeast of Columbus. No staff members were taken hostage.
Two of the guards were taken to a hospital after the 5 p.m. attack. One suffered head injuries and bruises and the other was being treated for shortness of breath.
The State Highway Patrol and tactical teams from the Rehabilitation and Correction Department later assembled to restore order.
Joe Andrews, a prison system spokesman, described the death-row unit as resembling a four-leaf clover and said the disturbance was in one leaf of the clover. The other three leaves were secure, he said.
He said 37 inmates were involved in the disturbance.