Stony Mountain Institution will be on lockdown until Thursday, according to officials with the prison.
Prison officials said it will take at least that long for guards to complete a search of cells after a fight that left seven inmates injured.
The fight at the medium-security federal prison just north of Winnipeg broke out Monday afternoon, prompting a lockdown.
Assistant warden Guy Langlois said a number of inmates were taken to hospital but none suffered any serious injuries and no prison staff were hurt.
Union spokesperson James Bloomfield said seven inmates were taken to hospital Monday.
Five of the injured suffered stab wounds and two sustained blunt-force trauma.
Visits to the jail have been suspended while RCMP and prison staff continue investigations.
"What the job is now is to take those weapons ... analyze them to see what type of materials they used to make them and then go back and try to find the missing pieces," Bloomfield said on Monday.
No charges have been laid at this time.