The Food and Drug Administration cracked down Wednesday on four manufacturers of caffeinated alcoholic drinks, giving them 15 days to stop adding caffeine to the products or stop selling them altogether.

The Food and Drug Administration (FDA) cracked down Wednesday on four manufacturers of caffeinated alcoholic drinks, giving them 15 days to stop adding caffeine to the products or stop selling them.

Dr. Margaret Hamburg, the FDA commissioner, said the drinks appeared to pose a serious public-health threat because the caffeine masked the alcohol’s effects, leading to “a state of wide-awake drunk.” She said the FDA decided caffeine in the drinks was an illegal additive.

In warning letters to the four companies — including Phusion Projects, which makes Four Loko — the FDA said drinking the beverages could lead to “hazardous and life-threatening situations.” The letters also warned that the FDA could move more aggressively, seizing the beverages from stores and asking a judge to halt further sales, if the companies did not take corrective action.

The other manufacturers warned were Charge Beverages, which makes Core High Gravity HG, Core High Gravity HG Orange and Lemon Lime Core Spiked; New Century Brewing, which makes Moonshot; and United Brands, which makes Joose and Max.

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Most of the products are carbonated malt beverages with fruit flavors and high levels of alcohol; Four Loko is 12 percent alcohol by volume and has up to 156 milligrams of caffeine per can, according to scientists who have analyzed it.

The Federal Trade Commission also took action against the four companies, warning that their marketing tactics might violate federal law and urging them to “take swift and appropriate steps to protect consumers.”

While the FDA reviewed more than two dozen makers of such drinks, agency officials said they were taking action against only four for now whose products seemed the biggest threat.

There have been numerous reports of young people falling ill after drinking the beverages. Four Loko came under scrutiny after students who drank it at Ramapo College in Mahwah, N.J., and Central Washington University in Ellensburg, Wash., ended up in emergency rooms. It has been blamed for several recent deaths.

The FDA announcement came a day after Phusion Projects said it would stop putting caffeine in its drinks.

Four states, including Washington, banned the drinks in recent weeks, and more are considering action.

Material from the Chicago Tribune is included in this report.