Police in west Quebec say they have broken up a major marijuana network in the region, one they allege hid grow-ops inside the basements of newly built residential garages.

A joint squad of provincial and regional police raided 10 residences on Thursday morning and searched other locations primarily in Gatineau, Montreal, L'Ange-Gardien, Lochaber Ouest, Val-des-Bois, and Notre-Dame-du-Laus.

Police arrested 21 people, including two men they allege were the ringleaders of the organization, which Sûreté du Québec Capt. Benoît Dubé had common ties to but no direct link to the Hells Angels.

Dubé said the yearlong investigation police learned the organization was building residential garages — about nine in total — in the region and adding basements with trap doors to house marijuana production facilities.

"You couldn't smell the production and you couldn't see the production. You had to know it was there," he said.

In an average year Dubé said the operation was producing about 2,500 pounds of marijuana and making about $3.9 million in profit from the production.

During the raids police seized:

More than $1.1 million in cash.

700 cannabis plants.

220 pounds of cannabis.

Two kilos of hashish.

23 firearms.

The investigation was a joint operation of Gatineau police, the Sûreté du Québec, the MRC des Collines-de-l'Outaouais with assistance from Revenu Quebec and Canada's financial intelligence unit, the Financial Transactions and Reports Analysis Centre of Canada (FINTRAC).