GREENBRIER, Tenn. (WCMH) – Police in Greenbrier, Tennessee are investigating the deaths of two teenagers believed to have been poisoned by a lethal cocktail of Mountain Dew and racing fuel.

Both boys, Logan Stephenson and J.D. Byram, were students at Greenbrier High School, WKRN-TV reports. They were reportedly among a group of teenagers in Greenbrier last Wednesday when the incident happened.

Stephenson, 16, was found unresponsive inside his home the next morning and pronounced dead at the scene. He is survived by his parents, grandparents and six brothers and sisters.

Byram was transported to Vanderbilt University Medical Center in critical condition where he died Monday night.

“Our hearts are heavy today as we have learned that a second young man has died from the incident last week,” said Sheriff Bill Holt. “We ask that everyone continue to pray for both of these families as they go through this tragic time.”

A vigil was held Tuesday night at Greenbrier High for the students. Dozens of students, family members and friends were in attendance.

The Director of Schools in Robertson County, Mike Davis, released the following statement:

On behalf of Robertson County Schools, I want to express our sincere condolences and heartfelt sympathies to the parents and families of two Robertson County Schools students who tragically lost their lives recently. Both were members of our Greenbrier High School student body. Our hearts go out to the families of each of these young men for their loss.

Two other Greenbrier High School students were taken to the emergency room after they reportedly told investigators they drank the racing fuel mixture. They were released and deemed OK.

The medical examiner’s office will be releasing a report about the teens’ cause of death within the next two weeks.

“I feel quite certain these people did not understand the potential lethality of this ingestion,” Donna Seger, medical director with the Tennessee Poison Control Center, told WSMV-TV.

Seger said this is the first time she has heard of the mixture, known as “Dew Shine.” PepsiCo distributes a non-alcoholic drink under the same name unrelated to the dangerous mixture.

Police said if you know someone who may have consumed a similar mixture to seek medical attention at once.

“You will not be in trouble with law enforcement if you were present at this gathering,” police said. “Our goal is to ensure the safety of our citizens and get medical help for those who may need it.”