ATLANTA (CNN/Gray News) – Nearly 80% of patients who suffered lung injury linked to vaping got their THC products from friends or online dealers instead of commercial sources, according to a new Centers for Disease Control and Prevention study.

“This study reinforces existing CDC and FDA recommendations that people not use THC-containing e-cigarette, or vaping, products, particularly from informal sources like friends, family, or in-person or online sellers,” CDC website says.

THC is the psychoactive compound in marijuana.

Teenagers under 18 are the most likely to get THC vaping products.

More than 2,600 people nationwide have been hospitalized with lung injury linked to vaping and 57 people have died.

Still, the CDC is not sure about the cause even though officials have been focusing on products that contain THC.

One possible culprit is vitamin E acetate, an additive used in some THC vaping products, but other chemicals haven't been ruled out.

The new report does not capture all the cases, but it does give the CDC a better idea about the products and sources associated with the outbreak.