The Food and Drug Administration has made a surprise inspection of the headquarters of Juul Labs, seizing “thousands of pages of documents,” according to release from the agency. The FDA called it an “unannounced on-site inspection.” Juul CEO Kevin Burns said that during the inspection, the company walked the FDA through “every part” of its business.

The company is under investigation for potentially marketing their e-cigarettes to children. Allegations have emerged that management knew the company’s e-cigarettes were widely popular with teenagers, but failed to make changes to its marketing strategy to reduce its appeal to underage users. The FDA said in a statement, “The inspection followed the Agency’s request for information that we issued to Juul Labs in April for documents that would help us to better understand the reportedly high rates of youth use and the youth appeal of Juul products, including documents related to marketing and product design.”

The FDA has declared war on the “epidemic” of underage vaping, based on FDA Commissioner Scott Gottlieb’s recent comments. Over the past year, the number of high school students who have used e-cigarettes in the past 30 days has climbed about 75 percent, according to preliminary data from the Centers for Disease Control and Prevention’s annual National Youth Tobacco Survey. That translates to nearly 3 million high school kids using e-cigarettes. The complete data set from the agency is scheduled to be published later in the year.

Burns has said the company plans to work with the FDA to prevent underage vaping. Burns commented, “We are committed to preventing underage use, and we want to engage with FDA, lawmakers, public health advocates and others to keep JUUL out of the hands of young people.” His statement continued, “We want to be part of the solution in preventing underage use, and we believe it will take industry and regulators working together to restrict youth access.”

The agency has cracked down on Juul in particular. The FDA says that it issued 1,300 “warning letters” and fines this summer to brick-and-mortar e-cigarette retailers busted selling Juul vapes to minors. Juul is the most popular of the hundreds of e-cigarettes on the market. According to Nielsen, Juul represented nearly 55 percent of the e-cigarette retail market as of March.