At least three people have now died from a lung illness that has been linked to vaping, with doctors calling it a “worrisome” trend, the Centers for Disease Control and Prevention said Friday. Health officials said no consistent e-cigarette products have been tied to the disorder. According to the CDC, a teenage Indiana patient died on Friday, in addition to the previously reported deaths in Illinois and Oregon. A spokesperson for the health organization said a fourth death is still under investigation, and officials are reviewing 450 possible cases linked to vaping across 33 states.

“There is clearly an epidemic that begs for an urgent response,” Dr. David C. Christiani wrote in an editorial published Friday afternoon in The New England Journal of Medicine.