A new study shows that toxic chemicals may be to blame for the outbreak of vaping related illnesses.

Mayo Clinic looked at lung biopsies from 17 patients who had lung injuries suspected to be caused by vaping.

Researchers found no evidence that the build-up of fatty substances from oils caused the injuries, which had been considered a possible culprit.

Instead, the biopsies showed chemical injuries, similar to what exposure to toxic fumes would cause. 

One doctor at Mayo Clinic's headquarters in Rochester, Dr. Taylor Hayes, said to avoid vaping, especially when it comes to products containing THC, the psychoactive compound in marijuana. 

"The majority of cases of lung injury used solutions that contained THC, but not all of them," Hayes said. "70% to 80% do, but then another 20% to 30% do not. Whether or not that's simply that they didn't report it or the report was incomplete, we don't know."

At least 26 people have died as a result of using e-cigarettes and vaping products, including two patients from the study, the CDC said.