Canada's biggest banks are jumping into the marijuana business.

The Bank of Montreal and the Canadian Imperial Bank of Commerce provided an $80 million loan this week to PharmHouse Inc, a joint venture owned in part by Canopy Rivers, the venture investment arm of publicly traded Canadian marijuana cultivator Canopy Growth.

The deal marks the largest debt financing provided by top banks to a private marijuana company.

"Having secured what we believe to be the largest bank debt to a private company in the cannabis industry, one that is supported by a syndicate of three Schedule I banks, PharmHouse has gained substantial momentum," said Canopy CEO Bruce Linton in a press release.

Though Canada legalized marijuana federally in October, most of the country's biggest banks have been reticent to enter the industry as they hold significant assets in the US, where marijuana remains illegal at the federal level.

In the past, the marijuana sector in Canada has been dominated by smaller investment banks, like Canaccord Genuity and GMP securities, who have led or co-led the most deals in the space.

But bigger banks are starting to take notice.

The Bank of Montreal advised Aurora Cannabis on its $2.3 all-stock merger with Medreleaf in May, among other smaller M&A transactions.

The Royal Bank of Canada also initiated coverage of the sector in December, and the bank's capital markets group said it would begin advising marijuana companies on stock sales and reverse takeovers.

"With two of the country's five biggest banks lending to the cannabis sector, the PharmHouse deal signals that the others aren't far behind," said Chuck Rich, a partner at the law firm Cassels Brock & Blackwell LLP, who advised PharmHouse on the loan. "Canada's big banks are open for business."

Canopy Rivers, for its part, has been active this month. The firm took part in a $12.1 million Series A funding round for Headset, an analytics startup for the marijuana industry.