The probe dubbed Project Greymouth began in August 2013 to gather evidence of illegal drug trafficking.
It's alleged that cocaine and methamphetamine were imported directly from Mexico then transferred to traffickers in several Ontario communities, including Oxford County, Norfolk County, Middlesex County, Waterloo Region and the Greater Toronto Area.
Police say Project Greymouth was then linked to an investigation carried out by Waterloo regional police, dubbed Grimm.
Thirteen search warrants were executed at a number of southern Ontario locations and police say 12 kilograms of cocaine and 3.5 kilograms of methamphetamine were seized, along with one stun gun, four vehicles, almost C$90,000 and US$38,000.
Twelve people have been charged with 49 offences, including charges relating to the Controlled Drug and Substances Act.
Police say several of the accused have appeared at the Ontario Court of Justice in Kitchener-Waterloo and Norfolk County.
An arrest warrant has also been issued for Peter Knelsen, who is believed to be out of the country, and police say the investigation is continuing.
"This joint investigation means thousands of dollars have been taken out of a criminal enterprise and prevented illegal drugs from getting into the hands of our young people," said OPP Deputy Commissioner Scott Tod.