Marty Katz / Redux / The New York Times Wendy Crossland with a picture of her daughter, Anais Fournier, who died last year of cardiac arrest, in Hagerstown, Md., Oct. 22, 2012.

One family is suing an energy drink maker after a 14-year old died soon after consuming the caffeinated beverages.

In the last three years, five people died after downing highly caffeinated Monster Energy drinks, according to information released by the U.S. Food and Drug Administration (FDA). The agency has not confirmed that the energy drinks were directly responsible for the deaths, but the voluntary reports to the FDA are part of 37 adverse events sent in by the public involving Monster drinks. The agency says it is investigating any potential health risks associated with the caffeine content of these beverages.

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Parents of 14-year-old Anais Fournier filed a lawsuit against Monster Energy claiming the caffeine in the company’s drinks killed their daughter. Fournier reportedly consumed two 24-oz. Monster Energy drinks in 24 hours and her autopsy attributed her death to “cardiac arrhythmia due to caffeine toxicity.”

The lawyer for Fournier’s family, Kevin Goldberg, obtained the adverse event reports collected by the FDA’s Center for Food Safety Adverse Event Reporting System under the Freedom of Information Act. Fournier had an underlying heart condition, but Goldberg told the New York Times her physician had not advised her to curb caffeine use or activity.

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According to the Times, between 2004 to June of this year, the FDA received reports of five deaths linked to Monster, an additional death related to another energy drink, as well as other side effects such as stomach pain, vomiting and abnormal heart rates linked to energy drinks, which include Monster and brands like Red Bull and Rockstar. Bloomberg reports that emergency room visits involving the beverages have soared 10-fold between 2005 and 2009.

In response to the lawsuit, Monster Energy spokesman Evan Pondel said in a statement:“Over the past 16 years Monster has sold more than 8 billion energy drinks, which have been safely consumed worldwide. Monster does not believe that its beverages are in any way responsible for the death of Ms. Fournier. Monster is unaware of any fatality anywhere that has been caused by its drinks.”

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The FDA says that because the adverse reporting system is voluntary, the agency cannot rule out other potential causes of death, such as health conditions or drug or alcohol use. But the system is often a harbinger of potentially harmful ingredients in food or beverages; in this case, the reports are prompting calls for the FDA to take a more rigorous look at the amount of caffeine included in energy drinks. Currently, the FDA does not require the amount of caffeine in a product to be listed on the food label. Since caffeine is not considered a nutrient, it only needs to be listed under ingredients if it is added to a food. Energy drinks aren’t regulated under FDA guidelines because they are sold as dietary supplements. And if they did fall under the FDA’s authority, the beverages would far exceed the levels that the agency considers safe — the FDA allows sodas to contain 71mg of caffeine per 12 oz., and requires makers to prove safety of any higher amounts. Energy drinks can contain anywhere from 160mg to 500 mg of caffeine per serving, according to the FDA.

Illinois Democratic Senator Richard J. Durbin, however, has pushed the agency to enforce caffeine levels in energy drinks as well as investigate potential dangers from additives in the beverages. In August, New York attorney general Eric T. Schneiderman also began probing energy drink makers over how faithfully they disclose all their ingredients to consumers.

The challenge for these efforts will be to find a threshold for defining toxic levels of caffeine in foods or beverages. Toxicologists told ABC News said that 5g to 10g of caffeine can typically cause death, but other factors, such as a person’s weight, pre-existing medical conditions and medication use, can bring that level down. It just remains to be seen whether that threshold comes anywhere close to levels reached by drinking several servings of energy drinks.