The Food and Drug Administration (FDA) said last week that it told about 30 manufacturers of alcoholic drinks that contain caffeine they would have to prove the beverages are safe for consumption.

“The increasing popularity of consumption of caffeinated alcoholic beverages by college students and reports of potential health and safety issues necessitates that we look seriously at the scientific evidence as soon as possible,” said Dr. Joshua Sharfstein, principal deputy commissioner of food and drugs, in a statement.

Of the combined use of caffeine and alcohol among U.S. college students in the few studies on this topic, the prevalence was as high as 26 percent, according to the FDA.

If the manufacturers cannot prove the safety of their products, the FDA threatened to remove the items from marketplace shelves promptly.

The drinks typically combine malt liquor or another type alcoholic drink with caffeine and fruit juices. These can be up to 10 percent of alcohol concentrations.

The FDA alerted manufacturers to the fact that the agency is considering whether caffeine can lawfully be added to alcoholic beverages. The agency said it is unaware of the basis upon which manufacturers may have concluded that the use of caffeine in alcoholic beverages is “generally recognized as safe” or prior sanctioned.

To date, the FDA has only approved caffeine as an additive for use in soft drinks in concentrations of no greater than 200 parts per million. It has not approved caffeine for use at any level in alcoholic beverages.

The companies warned have 30 days to produce evidence, with supporting data and information, to conclude that the use of caffeine in their products is safe.

In late September, the FDA received a letter from 18 Attorneys General and one city attorney expressing concerns about caffeinated alcoholic beverages.