Walmart Inc. will stop selling e-cigarettes in its U.S. locations as the country grapples with a string of vaping-related deaths.

“Given the growing federal, state and local regulatory complexity and uncertainty regarding e-cigarettes, we plan to discontinue the sale of electronic nicotine delivery products at all Walmart and Sam’s Club U.S. locations,” it said in a statement. “We will complete our exit after selling through current inventory.”

The decision comes after the U.S. Centers for Disease Control and Prevention said this week that 530 people have fallen ill from a mysterious vaping-related lung disease, and that seven people have died. Officials still haven’t determined a cause of the ailment, and there didn’t appear to be one product or substance involved. Cases have been identified in 38 states.

Walmart, which had been up less than 1 per cent, erased gains on the news. Shares of Altria Group Inc., the Marlboro maker that invested in e-cigarette maker Juul Labs Inc. last year, briefly pared gains on the news, but bounced back.

Earlier this year, Walmart already stopped selling cigarettes, including electronic ones, to buyers under the age of 21.

The recent round of illnesses have been reported most often in patients inhaling products with THC, the key psychoactive ingredient in cannabis. Some were using vaping and e-cigarette devices with both THC and nicotine, while a small number were using nicotine devices alone.

Vaping has also been at the center of a growing controversy over what U.S. regulators have described as an epidemic of underage use. Last week, the Trump administration said it would take steps to remove almost all flavored e-cigarette products from the market, pending their approval by the Food and Drug Administration.