Food and Drug Administration officials are investigating more than 13 deaths that have allegedly occurred after the consumption of the popular 5-Hour Energy drink.

Authorities said the deaths and other extreme side effects, which range from spontaneous abortion and cardiac arrest to convulsions and shock, may not have been related directly to taking an energy drink, but were experienced after consumption.

The FDA’s Center for Food Safety and Applied Nutrition oversees the Adverse Event Reporting System and reported that each symptom occurred with “products under the labels 5-Hour Energy, Monster, and Rockstar between January 1, 2004 and October 23, 2012.”

A total of 18 deaths were reported between the three products, including 13 linked to 5-Hour Energy and another five to the Monster energy drinks.

Living Essentials LLC, the Farmington Hills, Mich. based company which distributes 5-Hour Energy, said in a statement that it was “unaware of any deaths proven to be caused by the consumption of 5-Hour Energy.”

The company encourages “no more than two bottles of 5-hour ENERGY shots per day, spaced several hours apart,” and also said that “consumers who have caffeine sensitivities should consult with a physician before taking and can consider the ‘decaf’ version.”

According to the company, the drink is only intended for adults “who need an extra boost of energy,” but is not considered a beverage or an energy drink.

FDA officials view the product as a dietary supplement which is regulated by the Center for Food Safety and Applied Nutrition.