A person who contracted a serious lung disease after using a vaping device has died in Illinois.
It is being treated as the first death in the US that has been linked to the smoking alternative, which is especially popular with teenagers and young adults.
Illinois Department of Public Health said the patient, who was between 17 and 38 years old, had been taken to hospital when they fell ill after vaping.
Their name, hometown and the date they died have not been disclosed.
Earlier this week, the Centers for Disease Control and Prevention said 149 people nationwide had contracted a severe respiratory illness after vaping, but no deaths have been reported.
In Illinois, the number of people who have contracted a respiratory illness after vaping has doubled in the past week to 22.
Dr Ngozi Ezike, from the Illinois Department of Public Health, said: "We requested a team from the CDC to help us investigate these cases and they arrived in Illinois on Tuesday.
"The severity of illness people are experiencing is alarming and we must get the word out that using e-cigarettes and vaping can be dangerous."
All of the illnesses reported were in teens or adults who had used an electronic cigarette or some other kind of vaping device.
Doctors say the illnesses resemble an inhalation injury, with the lungs apparently reacting to a caustic substance.
Health officials around the country have been reporting patients getting sick after vaping, including two in Connecticut, four in Iowa and six in Ohio.
They are asking doctors and hospitals to tell state health officials about any possible vaping-related lung disease cases they encounter.
In the UK, Public Health England says on its website: "While not without some risk, when compared to smoking e-cigarettes are far less harmful [than smoking cigarettes].
"E-cigarette vapour does not contain tar or carbon monoxide, two of the most harmful elements in tobacco smoke. It does contain some chemicals also found in tobacco smoke, but at much lower levels."