More evidence from the Centers for Disease Control and Prevention links synthetic vitamin E oil added to illegal THC products to the spate of the vaping-related illnesses that have now sickened 2,290 people.

The new findings come as New York City becomes the latest large metropolitan area to ban flavored electronic cigarettes, joining a growing number of other cities and states in an effort to control another major vaping problem: underage vaping. Addiction experts insist that the kid-friendly flavors hook youth on the nicotine products.

In the report published Tuesday, investigators at the Minnesota Department of Health analyzed products containing THC, marijuana's psychoactive ingredient. Twenty product samples obtained from vaping illness patients contained vitamin E acetate, while 10 products gathered a year ago — before the outbreak was reported — did not contain vitamin E.

The CDC has reported steadily rising numbers of vaping-related illnesses, known as EVALI, over the past few months, though the increase in weekly cases appears to be slowing.

At least 48 people have died, and additional deaths are under investigation.

The new clues boost findings from the CDC released earlier this month, when investigators tested samples of lung fluid from 29 patients, finding vitamin E acetate in all 29. The patients were not clustered in one area of the country, rather, they were spread out in 10 states. And nearly all had reported vaping THC.

The oil had also been found previously in product samples provided by patients, though investigators say it's too soon to rule out other toxins or ingredients contributing to the EVALI cases nationwide.

Vitamin E acetate is found in many common products, from food to supplements to skin care lotions. There is no evidence that it causes harm when swallowed or applied to the skin.

Meanwhile, the bill in NYC bans sales of flavored vape products, including mint and menthol. It's expected to be signed into law.

"With this vote, the city council is moving to ban the fruity, minty, candy-like flavors of e-cigarettes which were clearly designed to appeal to young people in the first place," New York City Council member Mark Levine said in a statement.

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