Public health officials at the US Centers for Disease Control (CDC) identified a potential cause of EVALI, the vaping illness this week. The sickness, called EVALI, has injured more than 2,000 patients and killed at least 39 people.

Now, CDC officials are focusing on vitamin E acetate as a “potential toxin of concern.” The teams found the substance in all 29 samples of lung tissue from patients from 10 states.

Harmless in supplements and cosmetics when used as directed, researchers are now clarifying vitamin E’s role in vaped products—and it is concerning.

“We have a potential toxin of concern from biological samples in patients,” said Dr. Anne Schuchat, the principal deputy director of the CDC, on a conference call for media on Friday. “We are in a better place than we were a few weeks ago in terms of finding a culprit.”

Neither THC nor nicotine was in every sample the CDC tested. However, the samples all shared the vitamin E acetate.

Wary moves forward as cause of EVALI identified

However, experts from the CDC cautioned the public that there may be more than one cause of EVALI. Officials are also investigating various vaping devices. This is in line with recent research on vaping and heavy metals.

On the call, Schuchat said that experts need to confirm the link between vitamin E acetate and EVALI with additional research. She also reminded the public that vitamin E is generally safe otherwise.

“There is a big difference between putting vitamin E acetate on one’s skin or swallowing a vitamin E pill and inhaling vitamin E acetate in an e-liquid,” confirmed Schucat.

EVALI stands for E-cigarette, or VAping, product use associated Lung Injury. Most cases thus far have been linked to black market THC products.

On Friday the CDC said that it appears that fewer cases of EVALI are developing now. However, some states are hit harder than others—mostly states which have totally criminalized cannabis.

The CDC recommends that no one vape anything, especially until we understand the final cause of EVALI. However, they consider black market THC products the highest risk, with any THC products next in line.

They also say that no one should add vitamin E acetate to any e-cigarette or vaping products until its relationship with lung health is better understood.