Eight teenagers in Wisconsin have been hospitalized with serious lung damage after vaping, according to health officials.

All of the teenagers were hospitalized during the month of July, according to Children's Hospital of Wisconsin, the facility where the teens were treated. These patients experienced a number of respiratory symptoms — including shortness of breath, chest pain, cough and fatigue — in the days and weeks leading up to their hospitalization. Some of the teens needed medical assistance to breathe. The teens also experienced nausea, diarrhea and weight loss.

All of the patients reported vaping in the weeks and months before their hospitalization, according to Children's Hospital of Wisconsin. Doctors haven't identified the exact cause of the teens' illnesses.

"It was alarming to have, over a short period of time, eight previously healthy teens come in very sick, unable to breathe, with weight loss, looking as if they had some sort of chronic lung disease when they didn't," Dr. Louella Amos, a pediatric pulmonologist at Children’s Hospital of Wisconsin, told the Milwaukee Journal Sentinel.

Some of the teens reported buying vaping products, including nicotine and THC, on the black market, the Journal Sentinel reported.

In general, the health effects of vaping are not fully understood, the hospital said.

"The popularity of vaping is obviously skyrocketing among our kids and its dangers are still relatively unknown," Dr. Michael Gutzeit, chief medical officer of Children's Hospital of Wisconsin, said in a statement. "We don't have a lot of information about the long-term effects or even the short-term effects."

The Wisconsin Department of Health Services is investigating the illnesses and recently sent out an alert to doctors asking them to be on the lookout for more cases. Officials are interviewing patients about the types of vaping products they used.

Most of the sick teens have responded to steriod treatment and have been released from the hospital, but one patient is still hospitalized, according to CBS News.

In addition to the eight confirmed cases, six more possible cases of teens with lung damage tied to vaping are being investigated, the Journal Sentinel reported.

Originally published on Live Science.