Why it matters: The vaping-related lung disease outbreak in the US has risen to 530 confirmed and probable cases as the number of deaths reaches seven. With the spread showing no signs of abating, the Food and Drug Administration (FDA) has opened a criminal investigation into the illnesses.

Earlier this month, it was reported that four Americans had lost their lives to the mysterious lung disease caused by vaping. It had been suspected that a particular type of chemical, possibly vitamin E acetate, was to blame, though it’s also possible that substances extracted from marijuana or hemp, including THC, could be creating dangerous new toxins when combined with vape-liquid chemicals. But no single substance or compound has been linked to all of the cases so far.

Not long after reports of the disease arrived, the Trump administration announced that the FDA would require vape companies to stop selling flavored vape products until they get regulatory approval. But more incidents of the illness are being discovered—the number of cases has jumped by 50 in just one week.

The FDA says its criminal investigations arm is now exploring the supply chain of vaping products to identify the cause of the outbreak. Mitch Zeller, the director of the Center for Tobacco Products for the FDA, said investigators will not be pursuing any individuals or companies and are not focused on prosecuting anyone at this time.

The backlash against vaping products isn’t only being felt in the US. India has banned the sale, import, advertising, and production of e-cigarettes, while Chinese retailers have stopped selling Juul products.