"The findings were published on Wednesday in The New England Journal of Medicine and involved samples from 13 men and four women whose ages ranged from 19 to 67. About 70 percent had a history of vaping marijuana or cannabis oils."

"Medical investigators have been unable to identify exactly what is causing the lung damage, or even how many harmful substances are involved. They do not know whether the source is the liquids being vaped, or a toxin released from the materials used to make vaping devices. It is also unclear whether some devices used in vaping may be defective."