A person smokes a Juul Labs e-cigarette in this arranged photograph taken in the Brooklyn, New York. Gabby Jones | Bloomberg | Getty Images

The Food and Drug Administration seized "thousands of pages of documents" in a surprise inspection of e-cigarette maker Juul's San Francisco headquarters last week, the agency said Tuesday. The FDA is looking into the company's marketing practices as Commissioner Scott Gottlieb calls teen use of nicotine vaping devices an "epidemic." It builds on the agency's request in April for company materials related to how Juul products appeal to kids. The most recent inspection, conducted Friday, "sought further documentation related to Juul's sales and marketing practices, among other things," the FDA said in a statement. Juul CEO Kevin Burns said the company walked the FDA through "every part" of its business, including its marketing practices and age-verification tools used on its online shop. "It was a constructive and transparent dialogue," Burns said in a statement.

Shares of three Big Tobacco companies — British American Tobacco, Philip Morris International and Altria — all moved to session highs on the news. Juul, which controls about 73 percent of the market, has been at the center of the FDA's attention this year as e-cigarette use soars among teens. The inspection comes weeks after the FDA announced a crackdown that requires e-cig manufacturers, including Juul, to submit plans to address youth use of their products within 60 days. The agency also threatened to ban some flavored nicotine liquids, which critics say attract kids to e-cigarettes.