Two deaths have been connected with the mixture; two other teens have been hospitalized

Inside 'Dewshine,' the Deadly Mountain Dew and Racing Fuel Cocktail That's Claimed the Lives of 2 Tennessee Teens

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Another Tennessee teen has died after allegedly drinking a bizarre cocktail of racing fuel and Mountain Dew.

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Police in Greenbrier, Tennessee, are investigating the incident after Logan Stephenson, 16, was found unresponsive in his home last Thursday.

Stephenson is the second teen whose death is possibly connected to the bizarre mixture: J.D. Byram died Monday night at Vanderbilt University Medical Center. Both teens were students at Grienbrier High School, and were reportedly among a group of students experimenting with the cocktail last Wednesday. Two other students were taken to the ER after coming forward and saying they’d also drank the mixture, but have been released with a clean bill of health.

“I feel quite certain these people did not understand the potential lethality of this ingestion,” Donna Seger, medical director with the Vanderbilt University’s Tennessee Poison Center, told WSMV-TV. The cocktail, known as “Dewshine” (Pepsi distributes a non-alcoholic version of Mountain Dew with the same name), is apparently new: Seger said this was the first time she’d heard of it.

“It’s a mixture of Mountain Dew and then methanol in racing fuel,” she explained. “There’s a little bit of methanol in the alcohol you drink, and that’s said to cause the hangover. To drink straight methanol is really a recipe for disaster.”

Methanol, Seger tells PEOPLE, is extremely toxic: Even if someone had just a sip or two, “we’d send them to the hospital.”

“It’s not like you can drink a half a cup and be okay,” she adds.

“It’s affecting things on the cellular level,” Seger told WSMV-TV. “It’s threatening the eyes, can cause one to go blind.”

Byram was taken to the hospital after “the color of his skin had changed and he started having a seizure,” Greenbrier Police Chief KD Smith told WZTV. “His hands started drawing up.”

Per the CDC, methanol occurs naturally in humans, animals and plants; “fresh fruits and vegetables, fruit juices, fermented beverages, and diet soft drinks containing aspartame are the primary sources of methanol in the human body,” they explain.

“We have certainly seen methanol infections, but nothing like this. I mean, this was a product that was almost 100 percent methanol, which is quite unusual,” Seger told WKRN. The American Association of Poison Control Centers tells PEOPLE these are the only two deaths in the country associated with the mix. Police stress that autopsy reports are forthcoming and that the substance has not definitively been linked to the boys’ deaths.

In 2012, at least 20 people were killed and dozens were sickened in the Czech Republic after alcohol tainted with methanol circulated in the Eastern European country. Police officials believed that the poisoning was accidental, a side-effect of bootleg alcohol distributors trying to stretch their product. Critics blamed the deaths on government for its leniency toward bootlegging in Eastern Europe: At the time, illegally manufactured alcohol constituted 25 percent of the Czech liquor market.