Nearly four in five people who suffered vaping-related lung injury reported using products that contained THC, alone or combined with nicotine, prompting health officials to declare THC-packed cartridges often purchased on the black market "may play a role" in the outbreak.

The Centers for Disease Control and Prevention said of 514 injured patients who reported details on their use of vaping devices and e-liquids, 77% used products that contained THC, alone or combined with nicotine. Only 16% of injured vapers said they used nicotine-only products.

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In a separate report that examined a smaller group of vapers, health officials in Illinois and Wisconsin said about two-thirds of those injured said they used a product called "Dank Vapes," sold in cartridges and often obtained from nonretail sources such as friends, family members or street suppliers.

"These findings do highlight the predominate use of pre-packaged, pre-filled THC cartridges obtained through informal sources," said Jennifer Layden, chief medical officer and state epidemiologist at the Illinois Department of Public Health.

Layden said the mostly young male vapers typically used more than one brand. In addition to Dank Vapes, other users cited THC-containing brands such as TKO, Off White, Moon Rocks, Chronic Carts, Cookies, Smart Carts and Kingpen.

Thursday, the CDC reported the number of vaping-related lung injury cases jumped to 805 and the number of deaths to 12. The CDC report, from 46 states and one territory as of Tuesday, was an increase from last week when the tally was 530 cases and seven deaths.

The confirmed deaths include two in California, two in Kansas and one each in Florida, Georgia, Illinois, Indiana, Minnesota, Mississippi, Missouri and Oregon.

The Trump administration endorsed a ban of non-tobacco, flavored vaping products, and a growing number of states are working to ban or restrict the devices. Washington Gov. Jay Inslee directed state health officials Friday to enact a ban on flavored vaping products. Michigan and New York are banning flavored vaping products, and Massachusetts ordered a four-month ban on all vaping products.

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Dr. Anne Schuchat, the CDC's principal deputy director, said health officials are conducting a "complex investigation" that has reached nearly all states and involves a wide range of substances and products.

Public health officials have not publicly identified which ingredients in THC cartridges might be harmful. State health officials recover products from injured vapers and send samples to the Food and Drug Administration for testing.

Schuchat said people who want to avoid injuries should avoid vaping or e-cigarettes, especially products that contain THC, the psychoactive ingredient in marijuana.

The "Illinois and Wisconsin data were very compelling," she said Friday. "The outbreak currently is pointing to a greater concern around THC-containing products."

Still, she said, the CDC does not know whether THC cartridges are the only risky product harming a growing number of young adults who need hospital care to treat a pneumonia-like illness.

"There may be more than one thing or risk within some of these products, and we need to follow the data to their conclusion," she said. "At this time, we do not believe consumers can tell what’s in the product, and there is not sufficient enough information on labels to know anyway."

Gregory Conley, president of the American Vaping Association, said his organization urged consumers to stay away from black market THC products.

"For the last six weeks, we have been ringing the alarm, saying illicit THC cartridges need to be avoided," Conley said. "The CDC took far too long to release this finding, but something is better than nothing. No youth should vape, and both parents and teens need to know what product could send them to the hospital after one day of abuse."

Contributing: Jayne O'Donnell