15 states have identified over 120 cases of severe lung disease or pulmonary injury that may be linked to vaping.
The US Centers for Disease Control it is investigating the trend among people who use e-cigarettes.
States with the most cases include Wisconsin and Illinois, with 25 confirmed and 27 more under investigation. CNN reports that the New York State Department of Health said Friday it was "actively investigating" 11 cases. California is investigating 19 cases, while Indiana and New Jersey reported nine cases.
The CDC reported 94 possible cases of lung illness associated with vaping in 14 states from June 28 to August 15. Health experts have pointed to various substances in e-liquids that may harm cells or contain "dangerous chemicals,".
The full extent of e-cigarettes' short- and long-term risks are still unclear.