Thousands of cannabis plants with a street value of more than £6m have been seized by police in the Bristol area.
Avon and Somerset Police found more than 7,000 cannabis plants with a street value of £6.6m across the force area over the past three months.
A major effort to disrupt the supply of the Class B drug in Bristol and Somerset was started by police code named Operation Viscount.
Sgt Jon Bane said Bristol had a significant drugs problem.
He said raids had taken place in properties ranging from from million-pound Clifton homes to commercial premises in Knowle.
Sgt Bane added that cultivation of the plant was widespread: "It knows no social boundaries, it's everywhere in the city.
"Even when we've found big-scale factories the neighbours have told us 'I hadn't noticed it' or that 'there was no smell'.
"Of the 7,000 plants recovered, the vast majority of them have been found in Bristol.
"Most of the information we've received has come from anonymous tip-offs via Crimestoppers," Mr Bane added.
Operation Viscount was set up to tackle the large-scale production of the drug.