Shares in marijuana company Curaleaf fell nearly 9% Tuesday morning after the federal Food and Drug Administration accused the business of “illegally selling unapproved products” with unsubstantiated medical claims.

Massachusetts-based Curaleaf is among the biggest players in the market for recreational marijuana and CBD and claims it will be the very biggest after completing two huge acquisitions. The deals include the purchase of Portland company, Cura Cannabis, in an all-stock transaction initially valued at $950 million.

In a letter issued Tuesday, the FDA said Curaleaf had made unsubstantiated claims that CBD products sold online can treat cancer, Alzheimer’s disease, opioid withdrawal, pain and pet anxiety.

“We will continue to work to protect the health and safety of American consumers from products that are being marketed in violation of the law through actions like those the FDA is taking today,” FDA Principal Deputy Commissioner Amy Abernethy said in a written statement. She added that the FDA sees “potential opportunities” in CBD treatments and is evaluating its policies around such products.

The FDA told Curaleaf to “take prompt action to correct the violations cited in this letter” and said failure to do so may trigger legal action, including “seizure and injunction.”

“Curaleaf is fully committed to complying with FDA requirements for all of the products that it markets,” Curaleaf said in a written response.

“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.”

Curaleaf is buying the recreational marijuana portion of Portland-based Cura, marketed under the brand name Select Oil. Cura’s CBD business is slated to be separated in the transaction; Curaleaf would maintain its own CBD brand.

While 11 states, including Oregon, have legalized recreational marijuana, it remains illegal under federal law. Federal law allows sale of CBD so long as it contains extremely low levels of the psychoactive substance THC, which produces the high associated with recreational marijuana, but CBD is still subject to federal regulations governing medicinal claims.

The legal and regulatory complications have made the market for legal marijuana highly volatile. With Tuesday’s decline in share price, Curaleaf’s market value has fallen by 27%, $1.2 billion, since announcing the deal for Portland-based Cura in May.