Eighteen-year-old Kelsie Falk, a senior at Mission Hills High School, and her 20-year-old sister, Kylie, were detained, cited and released at their home in the 200 block of West La Cienega Road in San Marcos shortly after midnight Sunday, Lt. Jeff Maxin said.Deputies responding to a report of a rowdy party in the neighborhood found the street in front of the Falks' residence blocked by numerous vehicles. Inside and outside the house were scores of revelers, drinking and playing "beer pong," the lieutenant said.Word about the party spread fast on social media. "Deputies estimate there were nearly 100 people at the party, and none of the teens contacted were of legal drinking age," Maxin said. "One partygoer was so intoxicated, he was found passed out inside a car."The home was strewn with beer cans and liquor bottles, and sheriff's personnel also found marijuana and cannabis paraphernalia in the residence, according to Maxin.The deputies broke up the party and instructed the minors to arrange for rides home.The girls' mother a PTA president told 10News she and her husband are devastated and disappointed. At the time of the party, they had been out of town celebrating their anniversary. She told 10News the young partiers trashed their home and caused extensive damage. The Falk sisters were ticketed for violating a city "social host" law that prohibits property owners from allowing people under age 21 access to alcohol at private gatherings. They are facing a $1,000 fine. Neighbor Kristen Lee was away Saturday night and arrived home the next day. "There were still some scattered cars around which we don't normally see," said Lee. Lee had never heard of the social host ordinance but believes it should be enforced. "I mean, it's just too risky that something could happen to one of those kids," she said. "That's really for kids' safety that's why you shouldn't be doing it."