Shares of Monster Beverage plunged Monday after the company's energy drinks were cited in five deaths reported to the Food and Drug Administration.

Corona, Calif.-based Monster Beverage's (MNST) stock ended the day down 14% on the Nasdaq.

The FDA has received "adverse incident reports" of five deaths involving Monster energy drinks, although the administration has not established a direct link in any case, according to FDA spokeswoman Shelly Burgess.

"We're still looking into it," she told CNNMoney.

The reports, first disclosed by the New York Times, were requested under a Freedom of Information Act filed by the mother of a 14-year-old Maryland girl who died in December from heart problems after drinking Monster Energy on two consecutive days.

The Maryland girl, Anais Fournier, drank two Monster Energy beverages that contained a combined 480 milligrams of caffeine, equivalent to about 21 8-oz. servings of Coca-Cola or 19 8-oz. servings of Pepsi,, according to the lawsuit filed by Wendy Crossland and Richard Fournier in California Superior Court on Oct. 17.

In a statement issued last Friday, Monster Beverage said it was "saddened" by the death, but pledged to "vigorously defend" itself in court.

"Monster does not believe that its beverages are in any way responsible for the death of Ms. Fournier," the company said. "Monster is unaware of any fatality anywhere that has been caused by its drinks."

A lawyer representing Fournier's parents, Kevin Goldberg of Goldberg, Finnegan & Mester, LLC, did not comment beyond the lawsuit.