Corona beer maker Constellation Brands is pumping a further $4 billion in Canada's top weed producer Canopy Growth.

Constellation was one of the first major alcohol producers to put its money into marijuana business when it invested $200 million into Canopy last year.

But the latest announcement is by far the biggest investment in the industry.

Four point four (4.4) million people reported using weed in the first half of the year in Canada.

And the country will fully legalize the recreational use in October.

Analysts say that, by investing in weed production, Constellation and its rivals, Molson Coors and Anheuser-Busch, are trying to hedge their bets for the future as beer sales are stagnating, particularly among younger Americans.