Health officials in New York State said on Thursday that they are investigating a possible cause of a recent surge in severe vaping-related illnesses: a compound called vitamin E acetate.

The state Department of Health said in a news release that “very high levels” of the compound had been found in 13 samples from eight of 34 patients who have gotten ill in New York. The samples were analyzed as part of an investigation by the Wadsworth Center, a state laboratory.

This finding by no means ends the search for what is causing the illnesses, particularly given that vitamin E acetate has not been confirmed as a factor in the majority of cases in which patients have gotten sick in New York.

“That’s the best theory, or hypothesis, we have right now,” Dr. Howard Zucker, the New York State health commissioner, said in an interview. “We haven’t ruled out there isn’t something else in the vaping material.”