The Food and Drug Administration (FDA) is investigating whether e-cigarette companies are marketing their products illegally, according to The Washington Post.

The agency sent letters to 21 manufacturers and importers, asking them to provide information on when more than 40 products went on the market. Tobacco products introduced or changed after August 8, 2016 must receive FDA clearance before being sold. If the FDA determines products are being sold illegally, the manufacturers could face fines, seizures or a court order to take the products off the market.

The new actions are part of the FDA’s plan to address the epidemic of youth e-cigarette use, the agency said in a news release.

“The FDA remains committed to the potential opportunity for e-cigarettes to help adult smokers transition away from combustible cigarettes. But we cannot allow that opportunity to come at the expense of addicting a whole new generation of kids to nicotine,” said FDA Commissioner Scott Gottlieb, M.D.