WASHINGTON — The Food and Drug Administration issued warning letters Wednesday to four manufacturers of alcoholic energy drinks often consumed by college students, saying the caffeine added to their beverages is an “unsafe food additive.”

FDA Commissioner Margaret Hamburg said the combinations of caffeine and alcohol in the drinks is a public health concern and can lead to “a state of wide-awake drunk.” Evidence has shown their consumption has led to alcohol poisoning, car accidents and assaults, she said.

The government could eventually seize the products if the companies continue to make and market them. The companies have 15 days to respond to the letters and either explain how they will take their products off the market or defend their drinks as safe.

The government came under increasing pressure as college students have been hospitalized in recent months after consuming the drinks. The FDA said experts have raised concerns that the caffeine in the drinks can mask a person's feeling of intoxication, leading to risky behavior.