Sankt Gallen police say 12 people will be charged after they raided two marijuana growing facilities at the beginning of the year.
Nearly 9,000 plants and 300 kilos of marijuana were seized in the operation which has been described as "highly professional".
The police say the 12 men worked 24 hours a day in shifts for over a year.
In connection with the operation, border guards also seized 5,500 plant saplings.
In addition to drug offences, some of the accused will also face immigration charges.