The Food and Drug Administration (FDA) has received reports of 13 deaths over the last four years that may have involved the highly caffeinated drink 5-Hour Energy, The New York Times reports.

Last month, the FDA said it was investigating reports that five people have died since 2009 after they consumed Monster energy drinks. The investigation was announced after parents of 14-year-old Anais Fournier sued the company in connection with their daughter's death.

The FDA said it has not established a connection between the drinks and the deaths. The FDA can regulate caffeine levels in soft drinks. The limit in a 12-ounce soda is about 71 milligrams. The caffeine levels in most energy drinks exceed that level, because they are labeled dietary supplements.

According to the newspaper, since 2009, the FDA has received incident reports of more than 30 cases of serious or life-threatening injuries such as heart attacks and convulsions, which mentioned 5-Hour Energy. These reports do not prove the product was responsible for a death or injury, or contributed in any way to it, the article notes.

While Monster Energy, Red Bull and other energy drinks that come in a can, 5-Hour Energy is sold in a two-ounce bottle called a shot. According to an analysis by Consumer Reports, the product contains about 215 milligrams of caffeine. An eight-ounce cup of coffee generally contains between 100 to 150 milligrams.

Last year, the Substance Abuse and Mental Health Services Administration issued a report that found a sharp rise in the number of emergency department visits linked with the use of non-alcohol energy drinks, from 1,128 visits in 2005, to 13,114 in 2009. The report noted that energy drinks are marketed to appeal to youth, and are consumed by up to half of children, teenagers and young adults.

Caffeinated alcoholic beverages (CAB's) or Alcohol energy drinks (AED's) are premixed beverages that contain not only alcohol but also include caffeine and other stimulants. Read more about this important topic here.