Federal health officials are urging people not to use vaping devices amid of string of illnesses across the country and three confirmed deaths tied to use of the products, with another under investigation.

“While this investigation is ongoing, people should consider not using e-cigarette products,” the Centers for Disease Control said in a press statement Friday.

“People who do use e-cigarette products should monitor themselves for symptoms (e.g., cough, shortness of breath, chest pain, nausea, vomiting, abdominal pain, fever) and promptly seek medical attention for any health concerns,” the CDC statement added.

The CDC is probing vaping-related illnesses, with 450 confirmed or suspected cases in 33 states.

Four deaths resulting from vape-related respiratory illnesses have been reported, including confirmed cases in Indiana, Illinois and Oregon.

The New York State Health Department on Thursday reported 34 cases of “severe pulmonary illness” from patients who used at least one cannabis-infused vape products. But these patients also used a range of products and devices.

The lab test results showed high levels of vitamin E acetate in nearly of off the cannabis-containing samples. Vitamin E acetate is used to synthesize the vape fluid.

“There is clearly an epidemic that begs for an urgent response,” Dr. David Christiani of the Harvard T.H. Chan School of Public Health wrote in an editorial published Friday in The New England Journal of Medicine.

In its statement, the CDC said e-cigs “should never be used” by youths and young adults pregnant women or “adults who do not currently use tobacco products.”

“Regardless of the ongoing investigation, people who use e-cigarette products should not buy these products off the street and should not modify e-cigarette products or add any substances that are not intended by the manufacturer,” the statement adds.

Said Robert Redfield, the CDC’s director of control and prevention, “We are committed to finding out what is making people sick. All available information is being carefully analyzed, and these initial findings are helping us narrow the focus of our investigation and get us closer to the answers needed to save lives.”