The Food and Drug Administration warned four manufacturers and retailers about selling liquids used in e-cigarettes with labeling or advertising that make them resemble kid-friendly foods and even reference the popular children’s show “My Little Pony.”

The agency’s enforcement action on Thursday is the latest in a broad crackdown on e-cigarette sales and advertising to minors. Last week, the agency and the Federal Trade Commission went after 13 makers and sellers of liquids that look like juice boxes, candy, or cookies.