Federal health officials said 530 people have fallen ill from the mysterious vaping-related lung ailment that has raised alarms across the U.S., up from 380 confirmed and probable cases that the government reported last week.

Seven people have died from the illness, the Centers for Disease Control and Prevention said at a briefing Thursday. Officials said they still hadn't determined a cause of the ailment and that there didn't appear to be one product or substance involved in all instances. Cases have been identified in 38 states.

"We are leaving no stone unturned," said Mitchell Zeller, director of the Center for Tobacco Products at the U.S. Food and Drug Administration.

Parallel to the public health investigation, the FDA's enforcement arm has also opened a criminal probe focusing on the vaping industry's supply chain, Zeller said.

The sudden surge of vaping illnesses, combined with an explosion of underage use of e-cigarettes, has forced public health officials to rapidly reassess what had been lax regulation of the fledgling industry.

Around the U.S., doctors have now seen hundreds of cases where patients have shown up in the emergency room, suddenly stricken with dangerous respiratory damage. Their lungs looked like they'd been ravaged by a disease, or as if they'd been exposed to a noxious industrial chemical. The common denominator was that they had all recently used vaping products.

Over the past several years, there have been a limited number of similar case reports, raising the question of whether there might have been other older incidents that were missed. But the severity and number of recent cases suggest that something has changed in the vaping devices that people are using, doctors say.

The vaping illnesses have been reported most often in patients inhaling products with THC, the key psychoactive ingredient in cannabis.

Some patients with vaping-related lung illnesses have had an unusual finding in their lungs: immune cells called macrophages that were filled with oil. That could be because the cells are engulfing ingredients from vaping devices.

On Sept. 5, state health officials in New York pointed to vitamin E acetate as a likely culprit. But other doctors interviewed by Bloomberg said the culprit is still unknown.