Stony Mountain Institution was in lockdown on Monday night following an inmate assault in the afternoon.
The lockdown was put in place at about 1:30 p.m. and a search of the institution was being conducted.
Early reports were that it was a stabbing involving two people but Stony Mountain officials and RCMP could not confirm the nature of the injuries or how many people were involved.
RCMP are working with Stony’s security intelligence staff to conduct a full investigation, said media spokesman Guy Langlois.
"Criminal and disciplinary charges can be laid against any inmate or individual found to be involved in illegal activity or, in this case, inmate assault," he said.
Ambulances transported several inmates — the exact number was not disclosed — to hospital but the injuries were not considered serious.
A press release stated visits have been suspended for the medium-security prison until the search is completed.
"The safety and security of institutions is CSC’s (Correctional Service Canada) primary concern. Regular activities in the medium-security unit will resume as soon as it is considered safe to do so. Visitors who have already planned a visit to the medium-security unit are asked to contact the institution directly," the press release stated.
Stony Mountain Institution is a federal prison for male offenders located about 18 kilometres north of Winnipeg.