Vaping illness deaths rise to 34 as public health officials hunt for cause of outbreak

A deadly lung illness linked to vaping has taken the lives of 34 people across 24 states as public health officials and regulators struggle to identify a precise cause of the outbreak, the Centers for Disease Control and Prevention said Thursday.

The total number of probable cases is now at 1,604, with 125 new cases diagnosed and one new fatality over the last week, according to CDC data complied through Tuesday. Patients have been found in 49 states as well as D.C. and the Virgin Islands, according to the CDC.

The median age of patients who have died is 49, ranging from 17 to 75 years old. The CDC says data on age, sex, and substances used in vaping products will be released on Friday.

The CDC has dispatched more than 100 physicians and investigators since the lung disease started to emerge as a public health threat in July. To date, they have not identified one single culprit that's making people sick.

"The cases appear similar, but there might not be one common cause," Mitch Zeller, director of the Food and Drug Administration's Center for Tobacco Products, said Thursday in a presentation at a tobacco regulation conference in Washington, D.C.

The CDC is tentatively calling the illness EVALI, short for e-cigarette, or vaping, product use associated lung injury. Most patients have reported vaping THC, the active ingredient in marijuana, though health officials still have not identified what exactly in the vaping products is making people sick.

Doctors initially said the illness resembled a rare form of pneumonia, caused by oil in the lungs, but new research casts doubt on that theory.

Researchers at the Mayo Clinic published astudy Oct. 2 that said a mix of "toxic chemical fumes," not oils, may be what's making patients sick. They examined lung biopsies from 17 patients suspected of having the mysterious illness.

State and federal health officials are interviewing patients about what they're vaping. FDA scientists are testing products patients are using. While investigators search for a cause, officials are urging people not to vape THC products. 

Watch: Connecticut Gov. Ned Lamont on why states must work together to regulate vaping