The heavily-caffeinated Monster Energy Drink is being investigated by US officials for its reported link to five deaths and one non-fatal heart attack.
The Food and Drug Administration (FDA) is looking into claims that people had adverse reactions after they consumed the 24 oz (680ml) can, which contains 240 milligrams of caffeine.
It has three times more caffeine than an 8.4 oz (240ml) can of its nearest rival, Red Bull, and seven times the amount in a regular 12 oz (340ml) cola.
Although the FDA is investigating the allegations, which date back to 2004, the agency said the reports do not necessarily prove that the drinks caused the deaths or injuries.
"As with any reports of a death or injury the agency receives, we take them very seriously and investigate diligently," spokesperson Shelly Burgess said in a statement.
News of the FDA's investigation follows the launch of a wrongful death lawsuit in California, by the parents of a 14-year-old Maryland girl who died after drinking two Monster Energy Drinks in just 24 hours.
A post mortem examination found that Anais Fournier died of cardiac arrhythmia due to caffeine toxicity that impeded her heart's ability to pump blood.
She also suffered from an inherited disorder that can weaken blood vessels. Her parents claim Monster failed to warn about the risks of drinking its products.
"I was shocked to learn the FDA can regulate caffeine in a can of soda, but not these huge energy drinks," her mother Wendy Crossland told The Record Herald.
"With their bright colors and names like Monster, Rockstar, and Full Throttle, these drinks are targeting teenagers with no oversight or accountability."
However labels on the cans do state that the drinks are not recommended for children and people who are sensitive to caffeine.
Monster said last week that it was "unaware of any fatality anywhere that has been caused by its drinks".
The company is the market leader in the US for energy drinks with a 35% share, while Red Bull has 30% and Rockstar has 19%.
But the company's shares plunged \$7.59, or 14.2%, to close at \$45.73 in trading on Monday after news of the FDA investigation.