Meanwhile, the Food and Drug Administration revealed that its criminal investigations unit started tracking leads early on. Some affected people used e-cigarette products with THC, while others used nicotine ones or those with both THC and nicotine.
There have been vaping-related illnesses in 38 states and one USA territory, the CDC said. More than half of these diagnoses have been among people younger than 25, Schuchat said, and 16% have been among those younger than 18. One person has died in each Oregon, Indiana, Michigan, Minnesota and IL.
The CDC has, as of September 17, received reports of 530 confirmed and probable cases of vaping-related lung illnesses, and seven confirmed deaths.
Zeller also said the FDA has activated its law enforcement arm, the Office of Criminal Investigations for a parallel investigation to identify what is making people sick and how it's supplied.
Finding the source of the illness is proving to be highly challenging, Zeller and Schuchat said, with no single product, device or substance being common to all of the people who've developed the illness.
During a conference call between state health officials and the Food and Drug Administration (FDA), earlier this month, investigators said they'd found a chemical called vitamin E acetate in nearly all of the samples of THC e-cigs they had tested.
People who became ill experienced cough, shortness of breath and chest pain, and in some cases, nausea, vomiting, diarrhea and abdominal pain, health officials said.
Health officials urged people not to buy vaping products off the street or modify them.
Identifying compounds is only "one piece of the puzzle and will not necessarily answer questions about causality", he said.
But if you're an adult who's using nicotine-containing e-cigarettes, you should not revert back to smoking cigarettes; rather you should contact a health care provider who can discuss possible treatments, she said. The group has special investigative powers that can be helpful in cases like this, he said, stressing the FDA isn't seeking to prosecute individual vapers.
"We weren't expecting a big clinical signal because they've only been really popular since 2010 or 2012", said Dr. Laura Crotty Alexander, a lung specialist at the University of California at San Diego who has been studying vaping's effect on health since 2013.