Shadowy “Dank Vapes” and other mysterious THC cartridges have been linked to a rash of vaping-related lung illnesses in both Illinois and Wisconsin, health officials warned Friday.

“Dank Vapes appears to be the most prominent in a class of largely counterfeit brands, with common packaging that is easily available online and that is used by distributors to market THC-containing cartridges with no obvious centralized production or distribution,” state health officials from Illinois and Wisconsin wrote in a report the U.S. Centers for Disease Control and Prevention released Friday.

But Dank Vapes, like many black-market brands, might not be a single company, producer or distributor — if it’s a real company at all, according to an Inverse investigation published in August.

The CDC report isn't the first time the Dank Vapes brand has been mentioned by health officials since an outbreak of illnesses swept the U.S. this summer. The cartridges were also flagged by New York health officials earlier this month.

“Dank Vapes appears to be the most prominent in a class of largely counterfeit brands”

Health officials have also repeatedly said they suspect black-market THC cartridges are a potential culprit behind the illnesses, since vape enthusiasts have no way of knowing what’s in them, they’re not regulated, and they often come prepackaged.

“Of the patients who reported what products they used, THC-containing products were the most prominent link across patients, with only 16% reporting using only nicotine-containing products,” CDC Principal Deputy Director Anne Schuchat said during a press briefing Friday.

Still, the supply chain of those vaping products can be a bit nebulous, and the CDC still hasn’t come up with a firm culprit for the spate of hospitalizations, especially since many of those sickened also vape nicotine products or use several brands at once.

Since the first sicknesses cropped up earlier this summer, 805 cases and at least 12 deaths have been reported to the federal agency. In the meantime, the Food and Drug Administration has opened up a criminal investigation relating to the rash of illnesses.

Meanwhile, researchers in Illinois and Wisconsin said Friday that they took it upon themselves to interview 86 people who reported illnesses after vaping. They found a whopping 234 products with 87 different brand names had been used among the group, according to their report.

There was no single brand name reported among all patients, but Dank Vapes came up 66% of the time, according to health officials. The brand names Moon Rocks, TKO, and Off White were also mentioned.

The CDC said Friday that it has not yet discovered a common ingredient among all the vape products it’s tested, so it’s unclear what — if anything — might be making people sick from those specific brands.

In New York, health officials suspected vitamin E acetate in the vape cartridges might be to blame. NBC News sent a cache of cartridges to a cannabis testing facility and found both pesticides and vitamin E among nearly all of the illicit, black-market vape pens they tested.

Because so much about the cause of the illnesses has been in the air for weeks, places like Massachusetts have outright banned all vaping products, at least temporarily. Michigan and New York banned flavored vape products, and President Donald Trump threatened a similar measure nationwide. The CDC similarly urged Friday that vaping should be avoided — particularly with marijuana products.