The Food and Drug Administration (FDA) has issued a marketing and safety warning to five makers of e-cigarettes, Reuters reported Sept. 10.

The FDA said that company claims that e-cigarettes help people quit smoking are unsubstantiated and therefore violate the Federal Food, Drug and Cosmetic Act. It also stated that some of the companies sell other liquid drugs to be used as refills in e-cigarette cartridges, at least one which has not been approved for the US market.

An e-cigarette runs on batteries and relies on replaceable cartridges of liquid nicotine. The device vaporizes the solution so the user can inhale it.

According to Reuters, the five companies warned by the FDA include E-CigaretteDirect LLC, Ruyan America Inc., Gamucci America (also known as Smokey Bayou Inc), E-Cig Technology Inc., and Johnson's Creek Enterprises LLC. They have 15 days to reply to the FDA’s warning.

An FDA spokesman said that the agency will not decide on specific next steps until the companies respond.