NEW YORK — U.S. health officials reported a breakthrough Friday in their investigation into the cause of a mysterious outbreak of vaping illnesses.

A government lab found the same chemical compound in fluid taken from the lungs of 29 patients across the country, the Centers for Disease Control and Prevention announced.

The compound — vitamin E acetate — was previously found in liquid from electronic cigarettes and other vaping devices used by many of those who got sick.

Officials said this is the first time they’ve found a common suspect in the damaged lungs of patients.

“We are in a better place in terms of having one very strong culprit,” said the CDC’s Dr. Anne Schuchat.

But agency officials cautioned they cannot rule out all other toxic substances, and it may take animal studies to clearly show vitamin E acetate causes the lung damage that’s been seen.

More than 2,000 Americans who use vape have gotten sick since March, many of them teen and young adults, and at least 40 people have died.

Vitamin E acetate has recently been used as a thickener in vaping fluid, particularly in black market vape cartridges. While vitamin E is safe as a vitamin pill or to use on the skin, inhaling oily droplets can be harmful.

Many who got sick said they had vaped liquids that contain THC, the high-inducing ingredient in marijuana, with many saying they got them from friends or bought them on the black market.

About two months ago, New York drew attention to vitamin E acetate when the state’s public health lab discovered it in samples of vaping products from sick patients. In some instances, it made up more than half of the liquid in the cartridges.

The chemical has shown up in tests in other labs, too, including a U.S. Food and Drug Administration lab in Cincinnati.

For the latest test, the CDC used fluid extracted from the lungs of 29 patients in 10 states. They looked for a range of substances that had been found in various vaping devices, including nicotine, THC and other marijuana components, plant oils, mineral oil and cutting agents used on the black market.

The one substance that came up in all 29 patients was vitamin E acetate.

“To me what’s important here is both what they found, and what they didn’t find” said Scott Becker, head of the Association of Public Health Laboratories. “This was the only thing they found.”