Police have made a drug bust at a barn in Stettler after officers discovered one of the largest illegal marijuana grow-ops in Alberta's history.

Crews counted 3,284 individual pot plants worth an estimated street value of $4 million.

The joint investigation was carried out by the Alberta Law Enforcement Response Teams (ALERT), the Calgary police and Stettler RCMP.

RCMP had been called to a rural property for reports of a suspicious person on Oct. 21. The next day, officers found a three-stage grow operation inside a barn running off an industrial-sized generator. They also located three kilograms of recently dried bud.

Police seized two pick-up trucks equipped with hidden compartments believed to be used for smuggling drugs.

Offcers also found two pick-up trucks equipped with hidding compartments in slip-tanks that were used to smuggle the drugs. (ALERT)

This is one of the top five largest outdoor grow-ops uncovered in Alberta. The largest bust happened five years ago near Drumheller, Alta., when 3,854 plants were seized.

Officials arrested a 53-year-old man a 35-year-old woman at the home on the property. They both face charges relating to drug trafficking and illegal production.

This slip tank was used during the grow-op that saw more than 3,284 individual pot plants. (ALERT)

Neither of them had a valid Health Canada grow-op licence.

To report suspicious a suspected marijuana grow operation in your community, contact police or Crime Stoppers at 1-800-222-8477 (TIPS). Find out more about identifying a grow op on ALERT's website.