Kroger and Walgreens are joining Walmart and other retailers in discontinuing the sale of electronic cigarettes.

Kroger, which also owns Harris Teeter, Ralphs, Fred Meyer, and other store brands, said it is discontinuing the sale of the product due "to the mounting questions and increasingly-complex regulatory environment."

Walgreens said it made the decision "as the CDC, FDA and other health officials continue to examine the issue." A spokesperson for the grocer added that the decision is "reflective of developing regulations in a growing number of states and municipalities."

E-cigarettes have come under regulatory and public scrutiny as a mysterious, deadly vaping illness continues to claim lives. The Centers for Disease Control and Prevention has identified at least 18 confirmed deaths and 1,080 probable cases across 48 states and the U.S. Virgin Islands as of last Tuesday. Most patients identified vaped THC, the active ingredient in marijuana, according to the CDC. Seventeen percent said they exclusively used nicotine.

E-cigarettes have exploded in popularity over the past few years, particularly among teens. Critics of the product have argued that flavored e-cigarettes made by companies like Juul are designed to appeal to teens directly.

With usage rising to a level the FDA has called an "epidemic" and heightened scrutiny, the Trump administration is readying a federal ban on flavored e-cigarettes. Michigan, San Francisco, and Boulder, Colorado, have banned flavored e-cigarettes. Michael Bloomberg, the billionaire and former New York mayor, pledged $160 million to help enact similar restrictions around the country.

Walmart said in September it will stop selling e-cigarettes in its Walmart and Sam's Clubs location, citing "regulatory complexity." Rite Aid in April said it would stop selling e-cigarettes in all stores.

Retailers have been increasingly taking action to regulate the sale of controversial products before federal regulation has been enacted.

Walmart, Walgreens and Rite Aid earlier this year announced plans to raise the minimum age to buy tobacco to 21, after a dozen states had already done so through legislation.

Officials at Kroger and Walgreens confirmed both companies will continue to sell tobacco products in their stores.