Sgt. Marc Tessier said the 16 had failed to return to the cells in their wing and they were not co-operating with jail officials Wednesday at about 9:30 a.m. ET.
The lockdown ended peacefully just less than nine hours later.
Tessier said the inmates destroyed the room including televisions, beds and furniture. He also said there were many conflicting demands and no clear message from the inmates, who will be interviewed.
While police reported nobody was hurt, charges may be laid.
No correctional officer was taken hostage or injured as inmates covered both cameras and windows with sheets to block any view into the wing, the CBC's Ashley Burke reported.
Twelve police negotiators set up a command post inside the jail to determine the reason for the demonstration and jail officials locked the area.
Tessier said the wing was a small space without access to the rest of the jail so the demonstration is contained.
Gatineau police were also on hand to ensure the security perimeter around the jail while provincial police are inside.
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