Indiana’s health department is investigating eleven cases of a severe respiratory illness to see if they’re linked to e-cigarettes. Similar cases were also discovered in Illinois and Wisconsin.

Indiana health officials say six of those cases have been confirmed. The patients range in age from 16 to 65, and all say they used e-cigarettes before getting sick.

“The majority of them are adults, and there have been no deaths,” wrote Indiana State Department of Health spokesperson Greta Sanderson wrote in an email to Side Effects. Eight people are still hospitalized

Symptoms include shortness of breath and chest pain, along with weight loss, nausea, and abdominal pain.

Reports of similar illnesses have popped up recently across the Midwest.

Wisconsin has confirmed 15 cases and is looking into another 15. Illinois has reported six cases and is investigating another five.

Indiana officials say it’s unclear what vaping products may have a connection to the illnesses here. Tests for viral, bacterial, and fungal infections came back negative.