The highly caffeinated drinks have been cited in 18 deaths in recent filings with the Food and Drug Administration, The New York Times reported Wednesday.
Thirteen deaths over the past four years have been linked to the highly caffeinated drink 5-Hour Energy, federal health officials say.
The FDA last month received five reports of deaths mentioning energy drink Monster Energy.
FDA records examined by the Times found some 90 filings with the agency since 2009 that mentioned 5-Hour Energy. More than 30 of the reports involved serious medical issues such as heart attacks, convulsions and a spontaneous abortion.
The agency says it has inadequate scientific evidence to justify changing the way it regulates the ingredients in energy drinks. Because reports about serious health incidents are filed by the drink producers themselves, they sometimes contain insufficient information to determine what role, if any, the drinks had in the fatality reports, said Daniel Fabricant, director of the FDA's division of dietary supplement programs.
In 2009, more than 13,000 emergency room visits were associated with energy drinks, the Substance Abuse and Mental Health Services Administration reported.
The maker of 5-Hour Energy, Living Essentials, said in a statement it was "unaware of any deaths proven to be caused by the consumption of 5-Hour Energy."
It added that it took "reports of any potential adverse event tied to our products very seriously."
Some lawmakers are pressing the FDA to increase regulations on the product. The attorney general of New York state is looking into how the drinks are produced.