An inmate was taken to an outside hospital after being assaulted at Millhaven Institution near Kingston on Tuesday.
The Correctional Service of Canada (CSC) says the OPP and the institution are currently investigating.
No staff members or other inmates were injured during the incident at the maximum-level security federal institution.
The CSC says in order to improve practices aimed at preventing this type of incident, it will review the circumstances of the incident and take the appropriate measures.
