According to administrators from the Department of Health Services in Wisconsin and the Department of Public Health in Illinois, a total of 14 teens and young adults were recently hospitalized for lung damage and breathing problems most likely related to vaping, CNN reports.

E-cigarettes are often advertised as a healthier substitute to traditional cigarettes. But as more research surfaces on these battery-powered devices, it’s becoming clear that they are associated with their own negative effects. Studies have shown that vaping can increase cardiovascular disease risk and cancer risk as well as expose users to toxic metals.

What’s more, experts cite a growing amount of evidence that shows increased coughing and wheezing among young people who use e-cigs. (Some ingredients used for vaping contain chemicals that can potentially lead to lung disease.)

In Wisconsin, severe lung disease landed 11 young people in the hospital, and three youngsters in Illinois were hospitalized for severe breathing problems—such as coughing, shortness of breath, fatigue and chest pain—after vaping. As a result, Illinois’s department of public health is trying to determine the names and types of vaping products involved and where they were purchased.

Meanwhile, Thomas Haupt, a respiratory disease epidemiologist with Wisconsin’s Department of Health Services, said the individuals in that state who became ill were otherwise normally healthy. “In some cases, they actually had to go to the intensive care unit and were placed on ventilators,” he said.

Like those in Wisconsin, the folks in Illinois also had no prior history of pulmonary issues and experienced the same symptoms. This is why experts are trying to ascertain whether the illnesses originated from a vape product or e-liquid.

As investigators remain on alert for more hospitalizations, researchers have continued working to identify a common cause among the incidents.