The U.S. Food and Drug Administration said Tuesday it is cracking down on sales of e-cigarettes, specifically Juul products, to minors, and has already uncovered 40 violations. Juul products come in a slim, USB-chargeable e-cigarette form with flavors that include "crème brulée" and "cool cucumber" that have made them popular with young people, many of whom do not realize they contain nicotine, as MarketWatch has reported. The FDA said it will hold retailers accountable for continued violations. "This blitz, and resulting actions, should serve as notice that we will not tolerate the sale of any tobacco products to youth," FDA Commissioner Scott Gottlieb said in a statement. The FDA has also contacted eBay Inc. to ensure that the products are not sold to minors online. It is also contacting the manufacturers of e-cigarettes to hold them accountable. In the case of Juul, the FDA is requesting documents "related to product marketing; research on the health, toxicological, behavioral or physiologic effects of the products, including youth initiation and use; whether certain product design features, ingredients or specifications appeal to different age groups; and youth-related adverse events and consumer complaints associated with the products."