A $6.5-million marijuana grow-op dismantled north of Toronto was using personal licences to grow medical marijuana as a cover to cultivate thousands of illegal plants, police allege.

York Regional Police Service’s organized-crime bureau executed a search warrant July 27 at 570 Strawberry Lane in the Holland Marsh region of King township, after stumbling upon the industrial-scale grow-op during a safety inspection with bylaw officers a day earlier.

Complaints had been made to the city about the pungent smell coming from the rural property, and dogs that were roaming loose. Neighbours knew the property housed a medical marijuana grow-op, but figured it was legal because three Health Canada grow licences were taped to the front window of the home.

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During the inspection, it became evident to police that the grow-op – which spanned 22 industrial greenhouses – far exceeded the limits of those licences, which together allowed for a total of 875 plants to be cultivated at a time.

Officers from the bureau’s guns, gangs and drug enforcement unit seized 635 pounds of harvested cannabis and more than 4,000 plants in the raid, totalling a street value of $6.5-million. Because the property was licensed to grow 875 plants, police officers had to leave that many plants behind after the raid.

Open this photo in gallery York Regional Police officers execute a search warrant at a cannabis grow-op last month. York Regional Police

The bust highlights the continuing challenges posed by Canada’s two-tiered medical marijuana system – and the ways it is being exploited for organized crime.

Under the current Health Canada regulations, medicinal marijuana patients can get their medicine in one of two ways: They can order it online through a licensed producer, or they can grow it themselves (or designate someone to grow it for them). While licensed producers are strictly regulated, personal and designated growers are subject to very little scrutiny.

A Globe and Mail investigation last year found that there are about 600 “super-growers” across Canada with prescriptions permitting them (or their designated growers) to have on hand, at any time, at least 244 plants and 35 kilograms of dried bud – far more than any individual patient could feasibly ingest.

By comparison, the average patient consumes less than three grams a day, which, according to Health Canada’s calculator, would allow them to possess 10 plants and 450 g of dried bud.

Health Canada can’t say how many personal grow-ops exist in total across Canada. It acknowledged there could be as many as 28,000 personal or designated operations actively, and legally, harvesting millions of plants under old, grandfathered licences. But the department does not know, because it stopped keeping records for such grow-ops when there was a change to the regulations in 2014.

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These industrial-scale personal grows have been magnets for theft and violence. York Deputy Chief Tom Carrique, who is also co-chair of the Canadian Association of Chiefs of Police committee on organized crime, told The Globe last fall that there have been a number of shootings and homicides across Canada linked to “what would be considered legal business within the medical marijuana framework. There have been numerous homicides connected to these locations.”

In the Strawberry Lane bust, two men who police allege were maintaining the plants were arrested. Samkeo Vanvilay, 43, from Laval, Que., and Chi Chung Phan, 36, from Montreal, have been charged with producing marijuana, and possession of marijuana for the purpose of trafficking.

Deputy Chief Carrique said neither of their names was on the grow licences. He said the investigation is continuing and police expect to lay further charges.

Records show the property was purchased by Jin Yue Kwong and Sui Ling Zeng in 2016. Detective Sergeant Doug Bedford, who heads York’s guns, gangs and drug-enforcement unit, said the licences were not assigned to them either.

In a statement on Friday, York Police Chief Eric Jolliffe said police are too often “identifying personal and designated production licence holders that are growing excessive amounts of cannabis under Health Canada authorizations. The product is then diverted to the illicit market by organized crime groups to supply illegal dispensaries, export outside of Canada and trafficked in our local communities.”

When new cannabis regulations take effect this October, upon legalization, a provision will be added allowing Health Canada to refuse to issue or renew a personal medical marijuana grow licence if it "would likely create a risk to public health or public safety, including the risk of cannabis being diverted to an illegal market or use.”