He sent Walgreens a letter on Monday requesting a meeting with its management team. Last month, Gottlieb said Walgreens was the top violator among pharmacies that sell tobacco products. Some 22 percent of Walgreens locations inspected by the agency caught employees illegally selling tobacco products to minors, the FDA said in a press release at the time.

The agency named corporate-owned and franchise retailers who were allegedly found selling tobacco products to minors more than 15 percent of the time since the FDA started conducting inspections 2010. These retailers include Walgreens, Walmart, Kroger, 7-Eleven, Family Dollar, BP and Citgo. FDA Commissioner Scott Gottlieb said in a statement that he plans to ask these companies about what policies they have in place and what more they plan to do.

The Food and Drug Administration called out 15 retailers on Monday for allegedly selling tobacco products to minors and requested information from more than 40 e-cigarette companies the agency thinks may have illegally introduced new products onto the market.

Walgreens in a statement said it welcomes the opportunity. The drugstore chain said it has a "zero tolerance policy" regarding selling tobacco products to minors and any employee caught violating it is subject to immediate termination. Walgreens said it's also promoting tobacco cessation in its stores.

"Retailers are on the frontlines of these efforts to reduce the health consequences of tobacco use and nicotine dependence," Gottlieb said in a statement Monday. "Walgreens, and other retail chains, should take seriously not only their legal obligations, but also the substantial public health importance of preventing tobacco product sales to minors at their stores."

The FDA also sent letters to more than 40 companies the agency suspects may have introduced e-cigarettes to the market without first getting the FDA's permission. Starting in August 2016, the FDA has required manufacturers to submit new products for review before selling them.

Juul, the market leader, hit shelves in 2015. As Juul has gained popularity over the past year or so, dozens of look-a-like products have entered the market, possibly in violation of the FDA's policy. Gottlieb said some of these companies may be trying to "capitalize on the troubling popularity of products like Juul among kids."

"If tobacco products are being unlawfully marketed and sold outside the FDA's compliance policy, we'll take action," he said Monday. "We simply cannot tolerate this behavior and will take additional action as needed."

The FDA also sent warning letters to several companies for selling e-cigarettes without a label warning consumers they contain nicotine.

The agency is trying to stem what public health officials are declaring an "epidemic" of teen vaping, with about one-fifth of high school seniors last year saying they used e-cigarettes. Gottlieb laid out a plan in November to effectively ban convenience stores from selling fruity flavors, a policy he is expected to formally introduce within weeks.

A BP spokesman said the company does not own and operate any convenience stores in the U.S. but that it expects all of its marketers to comply with the law and will take appropriate measures when it believes they have not met expectations or contractual obligations. A spokeswoman for Family Dollar said the retailer takes reports like this "very seriously" and is "fully committed" to complying with tobacco sales regulations.