"They come in not breathing well and look very sick," Louella Amos, a pediatric pulmonologist with Children's Hospital, told the Journal Sentinel.
Jonathan Meiman, chief medical officer with the Wisconsin Department of Health Services, said the teens said in early interviews they had inhaled nicotine and THC.
"We have a common theme of vaping," Meiman told the Journal Sentinel. "We do not know of one product."
Nearly 3.6 million middle and high school students reported using e-cigarettes last year, WISN reported, quoting figures from the Centers for Disease Control and Prevention.
“Vaping in teenagers is something that's causing harm to our kids and we want that message to be loud and clear,” Dr. Michael Gutzeit of the Children's Hospital of Wisconsin told the television station.