Here in Western WA we had 55 homes raided last year including the house across the street from us, all part of a massive Chinese drug cartel. They buy houses with cash, and run massive growing and distriibution from them, right under the noses of the neighbors. We had no clue what was going on, other than they kept to themselves, and you would never see the drapes open.
The detectives told us they redo the ventilation having ducts run up the chimney to hide the smell, though we were smelling what we thought were skunks, when all the time we were smelling the pot. Once in a while they would have a UHall parked in the drive, but you never saw anything come and go from it. What they would do, is pack it up after midnight with the pot. News said the stuff was not sold locally, but instead driven to the East Coast.