Lung illnesses and deaths linked to vaping nationwide have continued to rise as federal health officials expand lab testing to understand the mysterious afflictions, the Centers for Disease Control and Prevention said Thursday.

As of Tuesday, the CDC has confirmed 33 deaths among 1,479 lung injuries associated with the use of e-cigarettes – up from at least 1,299 cases and 26 deaths announced last week. The cases span every state but Alaska, as well as the District of Columbia and one U.S. territory.

The numbers that have risen rapidly since the first death was reported in August have helped fuel a crackdown on battery-powered devices that simulate smoking. Health advocates have long raised alarms that products touted as a healthier alternative to cigarettes are getting youths addicted to nicotine, and the Trump administration plans to ban the flavored products often blamed for drawing in kids. Some policymakers are also citing the recent surge in vaping-related illnesses as they halt e-cigarette sales.

Announcing the latest increase in illnesses, the CDC reiterated its conclusion that products containing THC, the psychoactive component of marijuana, are a main culprit and should be avoided. About 78 percent of patients say they used vaping products containing THC, according to the CDC, and nearly a third of patients reported only using THC products. Ten percent said they only vaped nicotine, although doctors caution that people may be reluctant to admit to using marijuana.

Investigations suggest that THC-containing products bought off the street or obtained from friends, family and illegal dealers are particularly dangerous, the federal health agency said. Opponents of vaping sales bans have argued that new policies should target black market items rather than e-cigarettes as a whole.

But because the cause of the lung illnesses remains unclear, “the only way to assure that you are not at risk while the investigation continues is to consider refraining from use of all e-cigarette, or vaping, products,” the CDC says on its website.

Deaths confirmed by the CDC span 24 states: Alabama, California (three), Connecticut, Delaware, Florida, Georgia (two), Illinois, Indiana (three), Kansas (two), Massachusetts, Michigan, Minnesota (three), Mississippi, Missouri, Montana, Nebraska, New Jersey, New York, Oregon (two), Pennsylvania, Tennessee, Texas, Utah and Virginia.

The new numbers reinforce earlier findings that patients are largely male and young. About 4 in 5 people afflicted for whom demographic data is available are younger than 35, according to federal data. Patients range from 13 to 75 years old and have a median age of 23.

Those who have died tend to be older, with a median age of 44, the CDC said.

Federal and state health officials are studying the illnesses, which they say have not been linked to any one product. The CDC said Thursday that it is increasing its lab testing – part of an effort to look for harmful chemicals across a “continuum,” from the liquid in e-cigarettes to the vapor they emit to patients’ bodies, said Cassie Brailer, a spokeswoman at the CDC’s National Center for Chronic Disease Prevention and Health Promotion.

The CDC has recently been testing patients’ lung biopsies and autopsy specimens and is planning to test samples of blood and urine as well as fluid squirted into and then collected from the lungs. The agency says it has already received samples.

With questions remaining after the Food and Drug Administration’s testing of vaping products, the CDC will also be testing the vapor emitted by e-cigarettes – “very soon if its hasn’t started already,” Brailer said. The CDC has been conducting this kind of “aerosol emission testing” for a decade in its tobacco laboratory, she said, but is just now applying it to the lung illness outbreak.