Walmart on Monday raised the minimum age to purchase tobacco products, including e-cigarettes, to 21 years old.

The company is also in the process of discontinuing the sale of fruit-flavored e-cigarettes.

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Walmart on Monday stopped selling tobacco products, including e-cigarettes, to anyone under 21 years old.

The company announced plans in May to raise the minimum age for tobacco purchases from 18 years old to 21 years old. The change took effect Monday in all US Walmart and Sam's Club stores.

Walmart also said in May that it is in the process of discontinuing the sale of fruit- and dessert-flavored e-cigarettes, which research shows are preferred by minors.

Walmart made the changes to tobacco sales after receiving a letter from the US Food and Drug Administration regarding the sale of tobacco to minors.

"While we have implemented a robust compliance program, we are not satisfied with falling short of our company-wide goal of 100% compliance," John Scudder, Walmart US Chief Compliance and Ethics Officer, said in a May blog post announcing the changes. "Even a single sale to a minor is one too many, and we take seriously our responsibilities in this regard. So today, we sent a letter back to the FDA outlining additional measures we're taking to keep tobacco out of the hands of minors."

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Walmart said it plans to improve employee training to prevent the sale of tobacco products to minors, and crack down harder on employees who fail its "secret shopper" checks that ensure workers are following protocols.

Previously, employees who failed the tests were required to engage in extra training and instruction, but faced no disciplinary action.

That changed in April. Employees who fail the "secret shopper" tests will now be at risk of termination. The company said it plans to conduct 8,000 "secret shopper" checks in 2019.

Walmart's changes follow a spate of similar changes by various companies and lawmakers aimed at curbing tobacco usage by minors.

Walgreens announced in April that it would raise the minimum age for purchasing tobacco products to 21, not long after Rite Aid said it would stop selling all e-cigarettes and vaping products.