The Food and Drug Administration has put vaping giant Juul on notice with a pair of letters calling out the company for misleading statements about its products and ongoing targeting of teens. It is demanding written answers to a boatload of pertinent questions and expects Juul to respond within two weeks or risk “even more aggressive action” by regulators.

The specific claims being disputed by the FDA have to do with Juul positioning itself as a smoking cessation product. Now, it may be obvious anecdotally that vaping is a good way to wean yourself off smoking. But unlike nicotine patches and other products, there isn’t a lot of documentation on the complete risk associated with vaping — and with several people dead of vape lung, there would seem to be some worth considering.

“Companies must demonstrate with scientific evidence that their specific product does in fact pose less risk or is less harmful,” said Acting FDA Commissioner Ned Sharpless in a news release. “Juul has ignored the law, and very concerningly, has made some of these statements in school to our nation’s youth.”

Juul was reportedly directly targeting social media channels frequented by young people and, “despite commitments JUUL has made to address this epidemic, JUUL products continue to represent a significant proportion of the overall use of ENDS products by children. Some of this youth use appears to have been a direct result of JUUL’s product design and promotional activities and outreach efforts.”

In a recent congressional hearing about the risk of “electronic nicotine delivery systems,” or ENDS, evidence was presented that a Juul representative told students that the company’s products were “much safer than cigarettes,” “totally safe,” and that the “FDA was about to come out and say it was 99% safer than cigarettes… very soon.”

Representations like these were apparently made far and wide, among students certainly and also among Native American communities. They aren’t the kind of statements you can just say — tobacco cessation products are regulated, essentially medical products, and the FDA looks at them closely. Claims have to be documented and evaluated.

Juul seems to have been walking very close to the line in its public statements, and it’s likely that the company very carefully crafted these messages to convince people that its devices are good alternatives to smoking while not making any claims that would expose it to FDA attention. But they appear to have stepped over that line now and again and provoked exactly the kind of scrutiny they’d rather avoid.

“We request that you provide any and all scientific evidence and data, including consumer perception studies, if any, related to whether or not each statement and representation explicitly or implicitly conveys that JUUL products pose less risk, are less harmful, present reduced exposure, or are safer than other tobacco products,” the FDA told Juul.

Furthermore it asked Juul to explain why it uses a 5% nicotine concentration in its products, which could increase the likelihood of addiction, and why the company uses nicotine salts, a substance that reduces harshness and allows greater nicotine concentrations.

Likely independent of the ongoing investigation into lung problems seemingly caused by vaping, the FDA also requested “Aerosol particle size analysis of aerosol formed from your device,” “experimental design and data on pK studies from your device, your e-liquid, and combusted cigarettes,” comparisons between free nicotine and nicotine salt delivery, and “How the design and performance of your device and/or e-liquid, including the level, formulation, and delivery specifications of nicotine, affect lung deposition as related to the use and addictive potential of the product.”

In other words, tell us why you designed your product to be extra addictive and attractive to non-smokers, and whether this was in spite of knowing the substances created caused lung damage.

In a statement, Juul said that it was “reviewing the letters and will fully cooperate.”