The Centers for Disease Control and Prevention has identified THC as possibly playing a role in the recent outbreak of a mysterious vaping-related lung illness that has infected 805 people in the U.S. and killed 12 of them.

The agency in a Friday statement urged people not to use e-cigarette and vaping products, particularly those containing THC.

Of 514 patients who provided the CDC with data on the substances they used, 77% reported using THC-containing products and 36% reported exclusive use of THC-containing products. 

That compares with 16% who reported using exclusively nicotine-containing products. 

The CDC also reiterated, however, that the investigation is continuing and no single product or substance has been linked to all lung injury cases. 

The CDC's new report may have something to do with the downturn in cannabis stocks Friday.

Bank of America downgraded Canopy to neutral from buy and slashed its price target to $27 from $46. 

B of A analyst Christopher Carey said he saw the company as a long-term leader in the industry.

But he also expected a second-half pause in Canada's cannabis-industry growth. That pause could affect Canopy, and there's too much risk in the shares until estimates are reassessed, he said.