The Food and Drug Administration is investigating five deaths and one non-fatal heart attack that may have been caused by Monster Energy Drink, a highly caffeinated beverage.

According to the reports being analyzed, people have had adverse reactions after consuming the popular drink, which contains 240 milligrams of caffeine - seven times the amount of caffeine found in a 12-ounce cola. The drink is packaged in a 24-ounce can.

“As with any reports of a death or injury the agency receives, we take them very seriously and investigate diligently,” said FDA spokeswoman Shelly Burgess in a statement.

While the FDA is investigating the allegations, which date back to 2004, the agency is also stating that the reports do not necessarily prove the drinks caused the deaths or injuries.

The news of the FDA’s investigation follows a filing last week of a wrongful death suit in Riverside, California, submitted by parents of a 14-year-old girl who died after drinking two 24-ounce Monster Energy Drinks in 24 hours. The child’s parents insist Monster failed to warn consumers about the risks of drinking its products.

While an autopsy concluded she died of cardiac arrhythmia due to caffeine toxicity, the medical examiner also found the girl had an inherited disorder that can weaken blood vessels.

Monster Beverage Corporation, which describes Monster Energy Drink as a “killer energy brew” and “the meanest energy supplement on the planet,” puts labels on cans stating the drinks are not recommended for children and people who are sensitive to caffeine.

The company, based in Corona, California, did not immediately respond to calls seeking comments on Monday. However, they said last week that it is “unaware of any fatality anywhere that has been caused by its drinks.”

Although the FDA caps the amount of caffeine in soda to 0.02 percent, there is no such limit for energy drinks.

New York State Attorney General Eric Schneiderman issued subpoenas to energy drink makers like Monster in August, as part of the state’s investigation of the energy drink industry. Then in September, Senators Dick Durbin and Richard Blumenthal asked the FDA to further look into the effects of caffeine and other ingredients in energy drinks on children.

Based on reporting by The Associated Press.