New research shows that vitamin E acetate is likely the cause of lung injuries associated with vaping and e-cigarette use.

In a paper published December 20 in the New England Journal of Medicine, health officials found evidence of vitamin E acetate in the fluid of the lungs of 48 of 51 people who had developed (or died from) a vaping-related illness. For comparison, they looked at the lung fluid from 99 healthy adults who didn’t smoke, and they didn’t find any evidence of it.

The study, combined with evidence that has been slowly mounting for months, is enough to reach a definitive conclusion: “We can conclude that what I call the explosive outbreak of cases of EVALI [e-cigarettes or vaping product use associated lung injury] can be attributed to exposure to THC-containing products that also contained vitamin E acetate,” Anne Schuchat, the US Centers for Disease Control’s (CDC) principal deputy director, said in a teleconference yesterday.