Federal authorities said on Tuesday they were issuing 13 warning letters to companies that sell vaping products like liquid nicotine in packaging that may appeal to children, including products that resemble juice boxes and candy.

The joint action by the Food and Drug Administration and the Federal Trade Commission is the latest step by the federal government to crack down on the vaping industry, particularly on devices that are popular with teenagers.

Last week, F.D.A. officials said they had started an undercover sting operation targeting retailers that sell the popular Juul products to minors and had asked the maker, Juul Labs, to turn over documents related to marketing practices and health research.

The action on Tuesday, against a group of manufacturers, distributors and retailers, focused on products that the agencies said were aimed at underage users or could be accidentally ingested by children. The products, sold through multiple online retailers, have names like One Mad Hit Juice Box, sold by NEwhere Inc., and Vape Heads Sour Smurf Sauce, sold by Lifted Liquids, which look like Warheads candy.