The Centers for Disease Control and Prevention (CDC) announced that over 1,000 people became ill from vaping e-cigarettes, including 18 deaths. Now, research by the Mayo Clinic of Arizona suggests the lung damage may be the result of chemical burns.

The CDC announced that 77% of the injured vapers were using e-cigarettes with tobacco and THC products, and 17% were using only nicotine. The CDC partnered with state-based health care services and research hospitals to try to determine the cause of the recent spike in vaping lung damage cases.

The Mayo Clinic of Arizona is one of the first to release data derived from recent cases. The research team tested lung biopsy samples from 17 patients, including two who have since died from the condition. All 17 biopsies suggested that the lung injuries were most likely caused by “direct toxicity or tissue damage from noxious chemical fumes.” These fumes are generated from the vaporized e-cigarette liquids. Researchers said it does not appear that the build-up of lipids, reported earlier as a possible cause of the lung damage, was a factor in these 17 patients.

According to Dr. Larsen, the senior author of the study, “It would seem prudent based on our observations to explore ways to better regulate the industry and better educate the public, especially our youth, about the risks associated with vaping.”