U.S. state California announced Monday it is suing Juul, the country's largest electronic cigarette manufacturer, for illegally targeting minors with its marketing campaigns.

E-cigarettes have soared in popularity among young people since they were introduced about a decade ago. California law prohibits the sale of vaporizing products to persons under the age of 21.

A joint lawsuit filed by California Attorney General Xavier Becerra and his Los Angeles counterpart alleges that Juul Labs failed to meet its obligations to verify the age of its customers.

"Today, we take legal action against the deceptive practices that Juul and the e-cigarette industry employ to lure our kids into their vaping web," said Becerra.

"We will hold Juul and any other company that fuels a public health crisis accountable."

Read more: Number of vaping related deaths and illnesses continues to rise in the U.S.

The San Francisco-based firm also retained the email addresses of customers it had identified as minors in order to send them advertisements, according to the lawsuit.

Juul sales represent more than 64 percent of all e-cigarettes in the U.S.

The company has denied that its products – including mango, mint and creme brulee-flavored e-cigarettes – were aimed at minors.

Read more: Tech Breakdown: Are e-cigarettes harmful?

Ahead of a possible ban by health authorities, the firm this month pulled its mint-flavored products after a study found it was the favorite flavor among high school students.

It now sells only three flavors in the U.S.: two tobacco-flavored varieties and menthol.

U.S. federal regulators this summer opened an investigation into potentially "deceptive marketing" by Juul.

Juul said at the time it has "never marketed to youth" but said it regretted a 2015 marketing campaign aimed at 25-34 adults that "executed in a way that was perceived as appealing to minors."

"Juul adopted the tobacco industry's infamous playbook, employing advertisements that had no regard for public health and searching out vulnerable targets," Becerra said Monday. 

The lawsuit comes as the vaping industry is facing tough scrutiny amid a mysterious epidemic of lung conditions linked to e-cigarette use that has killed more than 40 people and sickened more than 2,000 in recent months.