Federal prosecutors in California are conducting a criminal probe of e-cigarette maker Juul, according to The Wall Street Journal.
According to the report, which cited sources familiar with the action, the probe is still in its early stages and the focus is not known.
A spokesperson for Juul was not available for immediate comment.
The percentage of teenagers who are vaping has doubled in the past two years, according to new federal data, which showed 25 percent of high school seniors reported using an e-cigarette in the past month.
Juul is facing multiple congressional probes and is also reportedly under investigation by the Federal Trade Commission over whether its ads were deliberately aimed at minors.
Lawmakers have also urged the Food and Drug Administration to pull most e-cigarettes off the market amid an outbreak of a deadly lung disease linked to vaping that has sickened at least 530 people and resulted in at least eight deaths.
Under pressure from the FDA, Juul last year shut down its Facebook and Instagram accounts. The company also pulled most of its fruity flavors from store shelves and will sell them only online.
Juul has maintained it never marketed to young people. It now focuses its marketing on adult users of traditional cigarettes, offering Juul as an alternative.