A 14-year-old girl from Maryland died last December after downing two Monster energy drinks in a 24-hour-period, according to news reports, and the incident is stirring concern over the safety of the beverages for kids.

It should be noted that the girl, Anais Fournier, had a heart condition, called mitral valve prolapse -- which means that one of her heart valves has malfunctioned. The National Institutes of Health reports that the condition is usually harmless, and as many as one in 10 people has a minor form of the condition.

After she drank two of the energy drinks -- which together contained 480 milligrams of caffeine -- she went into cardiac arrest a day later and died from cardiac arrhythmia due to caffeine toxicity, TODAY reported.

"She was at the mall with her friends the night before, and had a 24-ounce energy drink," Fournier's mother, Wendy Crossland, told the Record Herald. "She drank another one less than 24 hours later, even though she knew I do not allow them because I know they are bad for you. She went into cardiac arrest three hours later at home."

TODAY reported that the amount of caffeine Fournier drank in the two Monster energy drinks is about the same as that found in 14 cans of Coca Cola -- and is almost five times the recommended caffeine limit from the American Academy of Pediatrics.

Caffeine is a stimulant, and is found in a multitude of food products, from coffee, to chocolate, to sodas -- and the amounts found in those products usually are not enough to cause any harm to health, Medscape noted.

But caffeine poisoning is not uncommon in the U.S. TODAY reported that cases of caffeine poisoning have increased over the last few years, from 1,128 in 2005 to 13,114 in 2009.

A recent study in the journal Pediatrics showed that anywhere from 30 percent to 50 percent of teens and young adults drink energy drinks. Nearly half of the 5,448 reported caffeine overdoses in 2007 were in people younger than 19.

"The known and unknown pharmacology of agents included in such drinks, combined with reports of toxicity, raises concern for potentially serious adverse effects in association with energy drink use," researchers wrote in that study. "In the short-term, pediatricians need to be aware of the possible effects of energy drinks in vulnerable populations and screen for consumption to educate families."