Federal regulators Tuesday threatened cannabis giant Curaleaf with possible legal action for allegedly making unsubstantiated medical claims about the cannabidiol, or CBD, products on its website and on social media.

In a public letter, the U.S. Food and Drug Administration gave Massachusetts-based Curaleaf about two weeks to explain what it has done to correct alleged violations, including website claims that CBD has "properties that counteract the growth of spread of cancer" and is "linked to the effective treatment of Alzheimer's disease."

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"Failure to promptly correct these violations may result in legal action without further notice, including, without limitation, seizure and injunction," the FDA said in its letter, signed by compliance directors Eric Nelson and Donald Ashley, a former Justice Department lawyer and King & Spalding litigation associate.

In a statement, Curaleaf said it "is fully committed to complying with FDA requirements for all of the products that it markets. We can reaffirm that nothing in the letter raises any issues concerning the safety of any Curaleaf product. Curaleaf products are all derived from hemp and meet the requirements of the Farm bill."

Many of the claims cited by the FDA letter could not be found on the company's website Tuesday.

Curaleaf recently announced it is poised to become the biggest cannabis company in the world, based on revenue, with its planned acquisition of GR Companies Inc. Loeb & Loeb and Stikeman Elliott served as legal advisers to Curalee the cash-and-stock deal valued at $875 million.

Federal law bars the sale of food containing CBD or the marketing of CBD products as dietary supplements. But that hasn't stopped CBD-containing dog food, cosmetics, coffee and cookies from being sold in some places around the country. Sales of hemp-derived, marijuana-derived and pharmaceutical CBD are expected to top $2.3 billion by 2022, according to cannabis analyst company New Frontier Data.

Then-FDA Commissioner Scott Gottlieb issued an advisory in April warning companies that the agency would pursue CBD sellers making "egregious, over-the-line claims."

"The FDA continues to be concerned about the proliferation of egregious medical claims being made about products asserting to contain CBD that haven't been approved by the FDA," Gottlieb wrote. "The FDA stands ready to protect consumers from companies illegally selling CBD products that claim to prevent, diagnose, treat, or cure serious diseases, such as cancer, Alzheimer's disease, psychiatric disorders and diabetes."

The FDA that day, in conjunction with the Federal Trade Commission, issued warning letters to three companies that allegedly made unfounded claims about their products' benefits.

Acknowledging pressure from manufacturers and members of Congress, however, the FDA hosted a hearing in May to take public comments on potential uses and abuses of CBD. An agency working group is also studying ways that CBD-containing dietary supplements and food could be legally marketed.