MILWAUKEE (AP) — Wisconsin health officials said Friday they’ve linked vaping to 11 recent cases where teenagers and young adults developed severe lung disease that required hospitalizations.

Another seven cases that may also be linked to vaping are being investigated but have not yet been confirmed, health officials said.

“We strongly urge people to avoid vaping products and e-cigarettes. Anyone — especially young people who have recently vaped — experiencing unexplained breathing problems should see a doctor,” said Department of Health Services Secretary-designee Andrea Palm.

The health department said all the patients they interviewed reported vaping in the weeks and months prior to being hospitalized after experiencing shortness of breath, fatigue, chest pain, coughing, and weight loss. Officials said the severity of the cases varied and some patients needed assistance breathing.

Some of the patients improved with treatment but officials say they’re investigating whether the lung disease will cause long-term damage.

The counties with confirmed cases include Racine, Door, Walworth, Dodge, Waukesha, and Winnebago.

Investigators are trying to determine what type of vaping products were used in all the cases.

The health department said it is working with the Centers for Disease Control and Prevention, local health providers, and other states to make them aware of the hospitalizations in case they see patients experiencing similar symptoms.

Using e-cigarettes, often called vaping, has now overtaken smoking traditional cigarettes in popularity among students, according to the Centers for Disease Control and Prevention. Last year, one in five U.S. high school students reported vaping the previous month, according to a CDC survey .