Nov. 15, 2012  -- The federal government and the New York Attorney General's office are investigating after the Food and Drug Administration received claims that the drink 5-Hour Energy may have led to 13 deaths and 33 hospitalizations over the past four years.

The popular energy shot – which comes in 2 oz. packages and packs a powerful caffeine punch, equal to two cups of coffee -- led the way in this new and growing energy drink segment over the past eight years. Now government officials are investigating whether the product, made by Michigan-based Living Essentials, does much more.

"If someone is to use multiple cans, now is when we start to see some of the side effects," Dr. Sean Patrick Nord, USC Director of the Section of Toxicology, told ABC News. "You're getting astronomical amounts, 30 to 40 cups of coffee."

The recent FDA filings mark the second time in a month the administration has confirmed it is investigating claims that energy drinks are causing fatal reactions. In October, Monster energy, another popular drink that contains even more caffeine, was allegedly linked to five deaths.

The manufacturers point out that these are just claims, and there is no proven link between the drinks and the deaths.

In a statement overnight, 5-hour Energy said the product is "intended for busy adults." The company says its compact product contains "about as much caffeine as a cup of the leading premium coffee."

During an interview this September, Manoj Bhargava, the founder and CEO of 5-Hour Energy, told ABC News "Nightline" that when used as directed, the caffeine in his product doesn't do any harm.

"It's overblown. When it's in small quantities … It's like this -- water is good, but if you have too much you drown," he said.

Most experts say the fatal dose of caffeine for an adult would be almost impossible to drink – actually 50 to 60 times of what is contained in an energy drink. But critics worry about children with underlying heart problems drinking them, and are warning that energy drinks may be more hazardous than coffee because of the temperature.