CHICAGO (Reuters) - U.S. health investigators are casting a wide net to understand what is sickening hundreds of vapers across the country and still have not ruled out any product on the market, even as vaping industry officials highlight the potential role of illegal cannabis products.

A man uses a vape as he walks on Broadway in New York City, U.S., September 9, 2019. REUTERS/Andrew Kelly

Dr Dana Meaney-Delman is leading the U.S. Centers for Disease Control and Prevention’s investigation into the culprit behind at least five confirmed deaths and 450 reported cases of lung illness linked with use of the devices.

The agency is recommending that people refrain from the use of any electronic cigarette or vaping device until there is more conclusive evidence of a cause, she said in an interview.

“We’re trying to prevent any additional cases and deaths,” Meaney-Delman said.

She has reviewed data so far from 64 patients, including cases published on Friday in the New England Journal of Medicine as well as other reports. Eighty percent of those patients reported the use of tetrahydrocannabinol (THC), the psychoactive component of cannabis, she said.

On Friday, the U.S. Food and Drug Administration warned consumers against using vaping devices bought “on the street” or adding THC and other substances to products purchased in stores. E-cigarette manufacturers have distanced themselves from illicit “street vapes” and stressed that their products don’t contain the liquids under scrutiny.

“We agree with the FDA. If you don’t want to die or end up in a hospital, stop vaping illegal THC oils immediately,” said Gregory Conley, president of the American Vaping Association.

Meaney-Delman said investigators are not yet ready to distinguish between products. The data she has reviewed show that 60 percent of patients used both THC and nicotine, while 20 percent reported only using nicotine in their devices.

“We’re absolutely concerned about THC, but there’s a large number in our data that are reporting (use of) both nicotine and THC,” Meaney-Delman said. “There is no one product, device or substance that we can point to that is common among all these different patients.”

DOCTORS WEIGH IN

The CDC’s view has been reinforced by the American Medical Association, which on Monday urged consumers to stop using any sort of electronic cigarette until the investigation yields clear findings. The AMA called on doctors to inform patients about the potential dangers of the devices, including toxins and carcinogens.

An FDA spokesman said on Tuesday the agency has not changed its recommendation to consumers. The FDA has faced mounting pressure to curb a surge in teenage use of e-cigarette products. Last year the number of high school students using e-cigarettes shot up by 78 percent, a trend that coincided with the rising popularity of Juul e-cigarettes. Juul is 35 percent-owned by Altria Group MO.N.

Former FDA Commissioner Dr. Scott Gottlieb on Monday called for government regulation of cannabis products in an interview on CNBC, noting the possible THC link to the illnesses.

Meaney-Delman said state health officials are now going back to interview all patients about the products they used.

The CDC is also trying to match what its scientists are finding in tissue and fluid samples taken from patients’ lungs with substances the FDA is identifying in the products used by sick patients. Meaney-Delman said some of the samples are nicotine products and some are THC products from a variety of places.

In the meantime, the agency is instructing doctors to start asking patients about their vaping history and urging patients who vape to monitor themselves and seek medical attention for symptoms of cough, shortness of breath, chest pain, nausea and vomiting.

Meaney-Delman said the publication of chest X-rays and CT scans from affected patients in the New England Journal of Medicine should help doctors identify additional cases.

“That’s helpful so physicians can look at the imaging, which has been really important to these diagnoses, and compare patients they have in front of them,” she said.