A patient has died after developing a severe respiratory disease due to vaping, say health officials, in what may be the first such death in the US.
The US state of Illinois' health agency said the unnamed patient was between 17 and 38 years old.
It comes amid an outbreak of illness across the US that officials have linked to use of e-cigarettes.
The Centers for Disease Control and Prevention said on Wednesday 149 people nationwide have become ill from vaping.
"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," Illinois Department of Public Health Director Dr Ngozi Ezike said in a statement announcing the patient's death.
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He added that officials from the US Centers for Disease Control and Prevention (CDC) had arrived in Illinois on Tuesday to help investigate the death, as well as 22 cases of vaping-related lung illnesses in the state.
Those affected had symptoms including coughing, shortness of breath and fatigue as well as some cases of vomiting and diarrhoea.
The CDC, which is tracking a "cluster" of 149 cases across the country, says it is unclear if the illnesses are related, but that they do not appear to stem from any infectious disease.
"In many cases, patients have acknowledged recent use of tetrahydrocannabinol (THC)-containing product," the CDC said, referring to the active compound present in cannabis.
According to the Associated Press news agency, the death in Illinois is the first from a vaping-related illness in the US.
At least two other people have previously died in the US after their e-cigarette exploded in their face.