The Centers for Disease Control and Prevention (CDC) on Friday described a possible link between the current outbreak of vaping-related lung injuries and the use of THC-containing vaping products.

The CDC’s findings indicated that out of 514 patients with suspected vaping-related illnesses, 77 had self-reported that they had been using products containing THC, or using both nicotine- and THC-containing products.

THC, or tetrahydrocannabinol, is the main psychoactive compound in marijuana, responsible for users' "high" sensation.

CALIFORNIA VAPING DEATHS, ILLNESSES PROMPT STERN WARNING FROM OFFICIALS

“CDC has made it a priority to find out what is causing this outbreak of lung injuries and deaths and we’re making progress,” CDC Director Robert R. Redfield said in a news release. “We continue to work 24/7 with state partners and FDA to protect our nation from this serious health threat.”

Of those who self-reported, 77 percent claimed to have used THC- or THC- and nicotine-containing products, while only 36 percent reported using THC-containing products only. Sixteen percent, however, said they had used only nicotine-containing products.

The CDC added that the exact cause of the current outbreak of vaping-related illnesses remains unknown, and that its investigation continues. Complicating matters is the wide variety of substances and vaping products the patients have reported using, as well as their location.

“CDC has made it a priority to find out what is causing this outbreak of lung injuries and deaths and we’re making progress."
— CDC Director Robert R. Redfield, M.D.

A report concerning 86 cases, and filed by the state health departments of Wisconsin and Illinois on Friday, had found that 57 of those patients used THC vaping cartridges produced by a brand called Dank Vapes. The report also stated that because THC products are illegal for nonmedical use in these states (and others), and the majority of these products are obtained through friends, dealers or illegal means, it's possible some patients didn't disclose what products they'd used.

Amid the CDC’s ongoing investigation, the agency is urging for the public to refrain from using vaping products, and “particularly those containing THC.”

The CDC and the Food and Drug Administration (FDA), along with state and local health agencies, are still investigating the cause of the 805 vaping-related lung illness cases reported across 46 states and the U.S. Virgin Islands. As of Sept. 27, 12 vaping-linked deaths have been reported across 10 states.

Health departments in some states – namely New York and Utah – are also eyeing vitamin E acetate as a potential cause of illness in some residents there. Laboratory testing confirmed the substance, also known as vitamin E oil, was present in "nearly all of the cannabis-containing samples" obtained from some sickened patients in New York. Meanwhile, Utah health officials said 90 percent of the samples tested by a state laboratory contained the agent.

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Fox News' Madeline Farber contributed to this report.