Spencer Platt / Getty Images The federal government and the New York Attorney General's office have announced that they are investigating the popular energy drink after the Food and Drug Administration received claims that 5-Hour Energy has over the past four years led to 13 deaths and 33 hospitalizations.

New reports implicate an additional brand of energy drinks in deaths.

The U.S. Food and Drug Administration (FDA) confirmed on Wednesday to the New York Times that the agency has received 13 reports of deaths potentially linked to the high-energy drink 5-Hour Energy in the last four years. Health officials have been raising the alarm over energy drinks for their caffeine content, not all of which is accurately listed on the product, and the lack of regulation over the beverages. Because they are considered a dietary supplement, the drinks aren’t subject to the same strict regulations established by the FDA that govern foods.

(MORE: Are Energy Drinks Fatally Caffeinated?)

According to the New York Times:

Since 2009, 5-Hour Energy has been mentioned in some 90 filings with the FDA, including more than 30 that involved serious or life-threatening injuries like heart attacks, convulsions and, in one case, spontaneous abortion, a summary of F.D.A. records reviewed by The New York Times showed.

5-Hour Energy’s parent company Living Essentials did not comment on the filings, but told the newspaper in a statement that it was unaware of any deaths caused by the drink.

Combined with the five deaths mentioning another energy brand, Monster Energy, that the FDA received last month, the report raises serious questions about whether these beverages are being properly regulated and labelled, especially as the energy drink category continues to grow rapidly; retail sales climbed to $8.9 billion last year, up 16 percent, according to the Wall Street Journal.

Daniel Fabricant, the FDA’s director of dietary supplement programs, told the Times that it may be difficult for the agency to pinpoint the drink as the direct cause of these deaths because some reports may not contain enough information, or medical data could debunk the possibility. But the Times notes that the fatality reports citing 5-Hour Energy are relatively high considering that in 2010, the agency received 17 reports in the dietary supplement and weight-loss categories, which include nearly 50,000 products such as energy drinks.

5-Hour Energy can pack a big punch for a drink that comes in a two-ounce bottle known as a shot and contains high levels of caffeine, taurine (an amino acid that is linked to improved athletic and cognitive performance), and some B vitamins. As the Times explains:

The company does not disclose the amount of caffeine in each bottle, but a recent article published by Consumer Reports placed that level at about 215 milligrams. An eight-ounce cup of coffee, depending on how it is made, can contain from 100 to 150 milligrams of caffeine.

In July, New York Attorney General Eric T. Schneiderman subpoenaed major energy drink makers Monster Beverage, Living Essentials, and PepsiCo (which makes a similar product called AMP) to determine if they are accurately reporting all of their products’ ingredients on their container labels.