The City of Toronto began its crackdown on the proliferation of illegal marijuana dispensaries on Wednesday, going after the owners of the properties rather than the sellers of the products.

Letters from the city and the Toronto Police Service were sent informing landlords of buildings that contain dispensaries that the shops violate local by-laws and the property owners are subject to stiff financial penalties. Until the city sent out the notices, operators of the dispensaries expected to be the ones facing fines, as much as $50,000.

The scramble in Canada's biggest city to block the open sale of a drug that will be legalized next year illustrates the confusion that has reigned since the federal Liberals were elected on a platform that included legalizing pot for recreational use.

Story continues below advertisement

Toronto has seen a boom in dispensaries in the past six months unlike any other city in Canada, surpassing Vancouver. Some estimates peg the number of storefronts at more than 100. Mayor John Tory called the trend "alarming."

With Canada moving toward legalization, the dispensaries have been operating in a vacuum, many claiming to sell pot for medical purposes, but with few limitations on how they do business. Police were not taking action unless they received complaints about a particular shop. While proponents say the vendors are helping people deal with medical issues such as chronic pain and post-traumatic stress disorder, the sudden proliferation has alarmed the city.

"It's a scare tactic, trying to frighten landlords into breaking their leases with tenants or finding a way to break them," said Quito Maggi, the public affairs representative for the Cannabis Friendly Business Association. "Trying to shut this down now doesn't make any sense … when dispensaries are about to be legal."

Mr. Maggi said he had heard of five or six dispensaries whose landlords received letters, all of them in Toronto's west end. Social media sites have also listed several said to be targets. The Globe and Mail reached two dispensaries, but they declined to comment.

"As the Owner it is your responsibility and within your authority to take steps to stop the illegal use of your Property," the city's Municipal Licensing and Standards Division wrote to one landlord in a letter obtained by The Globe and Mail. "If you have not complied within 3 days of this letter further enforcement action may be directed at you."

It is not known how many letters were sent. The federal government's plan to legalize pot will begin with the introduction of legislation in spring 2017. In the meantime, it is still illegal.

One property owner also received a letter from Toronto Police on Wednesday about a marijuana dispensary.

Story continues below advertisement

"This unlawful activity is negatively affecting the health, safety and security of the community in a definable and excessive manner," the letter said. "As such; it is incumbent upon you as the registered owner to ensure that you are meeting your obligations as a property owner."

The blitz comes a day after members of the dispensary community held an emergency meeting at The Hotbox in Toronto's Kensington Market about how to fight the sanctions, including legal strategies.

The federal government has signalled concerns about keeping organized crime out of the new industry and ensuring the safety of some cannabis grown outside the medical marijuana sector, which is federally regulated.

It is unclear whether dispensaries will have to close or will engage in a legal battle to stay open.

Toronto Police Service could not be reached for comment on the letters on Wednesday night.