WASHINGTON  Top federal food regulators threatened on Friday to ban caffeinated alcoholic drinks unless their makers quickly proved that the beverages were safe.

In a statement, the Food and Drug Administration said it had told nearly 30 manufacturers of the drinks that unless they could provide clear evidence of safety, it would “take appropriate action to ensure that the products are removed from the marketplace.” Officials did not say how long such a determination might take.

The drinks, which combine malt liquor or other spirits with caffeine and fruit juices at alcohol concentrations up to about 10 percent, have become increasingly popular among college students. In a news conference, Dr. Joshua M. Sharfstein, the agency’s principal deputy commissioner, said their consumption was associated with increased risk of serious injury, drunken driving, sexual assault and other dangerous behavior.

The agency’s action was prompted by a letter from 19 state attorneys general, who expressed concern about the products’ safety.