Authorities arrested 20 teenagers and a 41-year-old woman early Sunday at a house party in Fort Mill, where they say teens were drinking beer late into the night.
The lead investigator called it one of the biggest underage drinking busts ever in York County.
When deputies arrived just after midnight at the home on Doves Road, they found teenagers hanging out in the backyard near two beer kegs and "a massive amount of empty cups," according to reports from the York County Sheriff's Office.
Bags of marijuana were found under the porch, reports stated.
Michelle Renee Boucher told authorities she hosted the party to celebrate her daughter's 18th birthday. Boucher bought the kegs at a beverage supply store near Carowinds, said Investigator Brian Schettler of the county's alcohol enforcement team.
The family recently moved to Fort Mill from the Charlotte area, Schettler said. That could explain why only two of the teenagers were from Fort Mill; the others were from Charlotte, Pineville and Matthews, N.C., arrest records show.
"Everybody there was drinking," said Schettler. "Usually, you'll find some that were drinking, some just there for the party. In this case, everyone was there to drink. Most were to the point they were intoxicated."
Boucher was charged with contributing to the delinquency of a minor and transfer of beer to a minor, according to a report.
The home is located off Sutton Road just west of Interstate 77.
Deputies learned of the party when they stopped a car on Sutton Road. Two teenagers and a 20-year-old man said they were leaving the party, deputies reported. Empty beer cans were found in the car, Schettler said.
Underage drinking has emerged as a hot issue in Fort Mill, where law enforcement officials say the problem is worse than anywhere else in York County.
Since January, more than 370 alcohol-related charges have been filed against minors across the county. An estimated 219 of those charges -- or 59 percent -- have been in Fort Mill Township, Sheriff's Office figures show.
Experts point to the affluence of Fort Mill to explain the trend. They say teenagers from wealthier families are more likely to drink beer and liquor at parties.
Fort Mill and Tega Cay have the highest median incomes in the county.