A mysterious vaping-related respiratory illness has killed five people across the United States, prompting health officials to urge vapers to give up their e-cigarettes and vape pens, at least temporarily.

Now, researchers in Utah claim they’ve identified a new connection between sufferers of “vape lung” — and it could help health officials finally get to the bottom of the strange sickness.

On Friday, the New England Journal of Medicine published a letter to the editor penned by investigators from the University of Utah. In it, the researchers detail their discovery of lipid-laden macrophages, a type of immune cell containing oily droplets, in the lungs of all six patients treated for vape lung at Salt Lake City’s University Hospital prior to the letter’s publication.

Since submitting the letter, the researchers examined the lungs of three more patients and found the cells in all three, according to a University of Utah press release.

“These cells are very distinctive, and we don’t often see them,” researcher Scott Aberegg said in the press release. “That made everybody start to think carefully about why they were there. Are they scavenging debris in the lungs that was introduced through vaping?”

A study focused on vape lung sufferers in Illinois and Wisconsin, which1 was published in the New England Journal of Medicine on Friday as well, also noted the presence of lipid-laden macrophages in seven out of 14 patients, adding further evidence that the cells play a role in vape lung.

“We need to determine if these cells are specific for the illness or whether they are also seen in vaping patients who are not ill and don’t have symptoms,” Aberegg said. “If they are only seen in patients who get sick, we can begin to make some connections between what we’re seeing in the lipid laden macrophages and whatever components of the vaping oils may be causing this syndrome.”

This isn’t officials’ first lead in the vape lung mystery — on Thursday, the Food and Drug Administration announced that it had found a chemical called vitamin E acetate in numerous samples of vaping products used by vape lung sufferers.

Still, every new connection investigators can identify between the more than 450 cases brings us one step closer to identifying vape lung’s true cause — and, hopefully, preventing it from claiming any more victims.