Health officials said Tuesday they have more evidence that a certain chemical compound is a culprit in a national outbreak of vaping illnesses.

Researchers analyzed black market vaping cartridges seized in Minnesota during the outbreak this year, and vaping liquid seized in that state last year. The newer cartridges contained the compound vitamin E acetate, but none of the older samples did.

They also looked at vaping cartridges collected from a dozen patients. Vitamin E acetate was commonly found in those, too.

The study was small, but it echoes other work that found the compound in the damaged lungs of 29 patients across the country.

“The findings further support a potential role for vitamin E acetate in causing lung injury associated with vaping products,” said Dr. Ruth Lynfield, a Minnesota health official.

Nearly 2,300 Americans who vape have gotten sick since March, many of them teens and young adults, according to a recent tally by the U.S. Centers for Disease Control and Prevention. At least 47 people have died.

Most who got sick said they had vaped liquids that contain THC, the high-inducing part of marijuana. Vitamin E acetate has recently been used as a thickener in illicit vaping products that contain THC, officials say.

(AP)