An inmate at Matsqui Institution in Abbotsford was airlifted to hospital Monday morning after being assaulted.
The Correctional Service of Canada (CSC) said the man was found injured at around 10:15 a.m., apparently the victim of an assault. He was evaluated by staff, then transported to an outside hospital.
Air ambulance, along with paramedics and fire/rescue crews attended the scene.
The prison was ordered into a lockdown and Abbotsford Police and prison officials are investigating.
"The assailant has been identified and the appropriate actions have been taken," the CSC said in a news release. Regularly scheduled visits may be affected and visitors are asked to contact the prison.
Matsqui Institution is a medium-security facility with capacity for 350 federal prisoners. Offenders receiving sentences longer than two years serve their time federally.