Juul Labs, the vaping company that has long insisted it never marketed its products to teenagers, purchased ad space in its early days on numerous youth-focused websites, including those of Nickelodeon, the Cartoon Network, Seventeen magazine and educational sites for middle school and high school students, according to a lawsuit filed Wednesday by the Massachusetts attorney general.

The suit, brought by the state’s attorney general, Maura Healey, presents some of the starkest evidence to date that the company was targeting young, nonsmokers during its launch period, from June 2015 through early 2016.

Juul executives declined to address the specific charges in the complaint. Instead, a company spokesman, Austin Finan, issued a statement that pointed to recent actions Juul has taken to combat underage vaping and said: “We remain focused on resetting the vapor category in the U.S. and earning the trust of society by working cooperatively with attorneys general, regulators, public health officials and other stakeholders to combat underage use and transition adult smokers from combustible cigarettes.”