The agency isn't targeting individuals for their personal use of controlled substances through the investigation, according to Mitch Zeller, the director of FDA's Center for Tobacco Products.
In the US, 380 confirmed or probably cases in 36 states and one territory.
As of September 17, there have been 530 confirmed and probable cases of lung disease associated with e-cigarette product use, or vaping, reported in 38 states and the US Virgin Islands.
A congressional subcommittee will hold a hearing on the outbreaks on Tuesday. The cases also include black market e-cigarettes.
John Felton, President/CEO of RiverStone Health and Yellowstone County's health officer, thanked the person associated with the first confirmed case for providing valuable information about their illness.
"I am concerned with the recent incidents of vaping related illnesses, as well as the high rates of vaping we are seeing among Saskatchewan youth", Reiter said. "We're very alarmed about products containing THC".
On Tuesday, New York became the first state to ban the sale of flavored e-cigarettes and other vaping products except for menthol and tobacco flavors. CDC hasn't said when people most people got sick.
Meanwhile, several TV networks - including CBS, WarnerMedia and CNN - say they will no longer air ads for e-cigarettes.
Still, health officials said they haven't found a definitive cause or a clear connection between cases, and they warned that patients anxious about becoming ill from vaping should refrain from using e-cigarettes.
The U.S. Food and Drug Administration is now investigating more than 150 products and substances and said it has activated its criminal investigations arm to explore the supply chain of vaping products and identify the cause of the outbreak.
Vitamin E acetate is suspected as a possible trigger for the disease - but it's only been found in THC vapes, which some, but not all of the severely ill patients used.
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. USA health officials also warned against altering vaping products sold from vendors. Seven deaths in six states have been attributed to the illness.
More than half the cases involved patients under 25 years of age and three-quarters were men, Anne Schuchat, the centers' principal deputy director, said.
In all confirmed cases, patients reported vaping within 90 days of developing symptoms, and most had vaped within a week of onset of symptoms.
