The number of people sickened with severe lung problems linked to vaping has doubled to 450 patients across 33 states.

There have also been at least three associated deaths — in Illinois, Minnesota and Oregon.

Dr. Tom Jeanne with the Oregon Public Health Division said the agency is trying to find any devices or products that were used by the person who died locally. Anything found will then be sent to the U.S. Food and Drug Administration for testing.

“It’s part of our standard procedures for an outbreak investigation to try to talk to anybody, family, friends or others who may have information,” Jeanne said.

Health officials are calling vaping-related illness an epidemic that demands an urgent response.

Dr. Dana Meaney-Delman, who’s leading the investigation for the Centers for Disease Control and Prevention, said a lot of questions remain.

“No specific e-cigarette devices or substances have been linked to all cases. And e-cigarettes include a variety of chemicals and additives and consumers may not know what each product contains,” said Meaney-Delman.

Her advice is plain: people should stop vaping.

“This is the primary means of preventing this severe lung disease,” Meaney-Delman said.

She said the CDC is working quickly to figure out what’s happening, but researchers still don’t know whether the problem is even new.

What they do know is that some patients had vaped cannabis, some had vaped tobacco and some had vaped both. Most had vaped within the last week and some had only vaped within the last 90 days.

All patients displayed similar symptoms, including gastrointestinal problems, fever and breathing difficulties. The symptoms are a lot like pneumonia, but there’s no associated infection. Instead, it’s a kind of pneumonia that happens when oils or lipids contaminate the lungs.

Dr. Daniel Fox, who’s seen a number of cases in his work at WakeMed Health in North Carolina, thinks doctors who suspect a case should be thinking about a diagnosis of lipoid pneumonia.

“It is a rare diagnosis,” Fox said. “We probably under-recognize it across all populations. But I think if there’s clinical uncertainty, that could be of some value to clinicians who are struggling to make a diagnosis.”

Lipoid pneumonia is usually found among people who work in areas where there is a lot of oil vapor, like a fry cook in a kitchen or workers at refineries.

Jeanne of the Oregon Public Health Division said he doesn’t know how long it might be until there’s an answer to what’s going on.

“Since this is a national-level investigation with more and more cases,” he said. “I think we’re going to have a large enough number to be able to say something conclusive. But I don’t know if that’s going to be in the next week or two or months down the road.”

Correction: A previous version of this story incorrectly identified a state where investigators think vaping related deaths have occurred. OPB regrets the error.