U.S. Sens. Richard Blumenthal (D-Conn.) and Richard Durbin (D-Ill.) recently sent letters to the CEOs of Monster Beverage Corp., Rockstar, Inc., and Red Bull North America, accusing the companies of marketing energy drinks to children. Citing “growing concern about the potential health risks posed by energy drinks,” the legislators claim that despite pledges to abstain from targeting children with direct advertisements, energy drink manufacturers have sponsored athletic competitions and professional athletes that appeal to youth.

In particular, the letters single out Monster Beverage Corp. for purportedly advertising on a Little League scoreboard; distributing free product samples at skate park events geared toward children; and sponsoring “Monster Energy Drink Player of the Game” awards for student athletes. Blumenthal and Durbin also highlight Rockstar’s sponsorship of “a 15-year-old professional skateboarder and role model to young fans” as well as Red Bull’s involvement with a high school football tournament and the Red Bull Rookies Cup, “a motorcycle race for children as young as 13 years old.”

“In light of public health concerns regarding the consumption of high levels of caffeine by children and adolescents and your company’s position that your energy drink products are not marketed to children, we are deeply concerned by evidence demonstrating direct marketing of your products to youth,” conclude the letters, which request a written response explaining why each company “is targeting marketing to children and what steps [are being taken] to prevent this type of marketing in the future.”