New York officials may have found an answer for the mysterious rash of illnesses linked to vaping that has already claimed three lives in the United States. On Thursday, the state’s Department of Health announced that it had uncovered lab results that identified “very high levels” of vitamin E acetate in “nearly all” the cannabis products they had examined in relationship to the vaping illness. Authorities say vitamin E is now “a key focus” of the investigation going forward.

“It is really starting to look like this is a cannabis vaping issue and that it may not have anything to do with e-cigarettes,” Michael Siegel of Boston University, who is a tobacco expert and public health professor, told USA Today.

Across the county, over 215 vape users have been hospitalized for breathing problems, and there have been three reported deaths to date, one in Oregon, one in Illinois, and one in Indiana. The condition has often been misdiagnosed as pneumonia, and patients have complained of cough, shortness of breath, chest pain, fatigue, fever and gastrointestinal distress such as nausea, abdominal pain, and diarrhea, among other symptoms. In New York, those who had been hit with the lung condition were mainly between the ages of 17 and 30.

New York Department of Health officials said that vitamin E acetate had been identified in each sample of cannabis products submitted by affected individuals. The Food and Drug Administration had also identified vitamin E oil in many samples submitted by patients.

“No one substance, including vitamin E acetate, has been identified in all of the samples tested,” said FDA spokesperson Michael Felberbaum to CBS News. “Importantly, identifying any compounds that are present in the samples will be one piece of the puzzle but will not necessarily answer questions about causality,” Felberbaum said. “The results from the FDA’s laboratory analysis will be shared with the respective states to aid in their investigations and will help further inform the federal response.”

Indiana has seen 30 incidents of the illness, which, similar to New York, has affected mostly people between the ages of 16 and 29. A study conducted within the state between 2012 and 2018 found that vaping was up 387 percent in high school students.

On Friday, Indiana’s Health Commissioner Kris Box told vapers to proceed with caution when using cannabis products.

“The tragic loss of a Hoosier and rising number of vaping-related injuries are warnings that we cannot ignore,” she said. “While it is unclear what substances are causing injury, when you use these products with other chemicals, you may not know everything that you’re inhaling and the harm it can cause.”

Concern over vaping, which appears to be replacing smoking for many US residents and has seen soaring rates among teenagers, has led some jurisdictions to ban e-cigarettes. Michigan became the first state to prohibit the sale of flavored e-cigs. In June, San Francisco — home to the corporate headquarters of Juul, the leading e-cig producer — announced a ban on the sale of e-cigarettes. Juul has spent $4.3 million so far on a ballot measure to overturn the ban, and is on track to break records when it comes to political spending on such a measure in the city.