Kiely was at the Prosser Family Campground on Friday night and was last seen around 12:30 a.m. Saturday, the Placer County Sheriff’s Office said.
“We are treating her disappearance as an abduction right now because we have not been able to locate her vehicle,” sheriff’s spokesperson Angela Musallam said.
Officials are looking for Kiely’s silver 2013 Honda CRV and say her phone has been out of service since the party. Kiely is White, 5’7″ and about 118 pounds. She has blond hair, hazel eyes and a nose ring. Kiely was last seen wearing a black tank top and Dickies brand pants.
There were 200-300 juveniles at the party, which was in a wooded area, Musallam said in a news conference Tuesday, and “someone knows something.”
“We are pleading, we are urging anyone who was at that party to please come forward,” she said.
“I can’t believe it. There has to have been one person — there were people sitting in cars, there were people everywhere around this place,” Kiely’s friend Sammi Smith told KCRA.
The grounds are about 17 miles north of Lake Tahoe and 36 miles from Reno, Nevada.
About 150 law enforcement officers, including the FBI, search and rescue, canines and more than 100 volunteers are combing the area around where Rodni was last seen.
“There is no evidence that supports an abduction, but we are not ruling anything out,” said Placer County Sheriff Troy Sander Tuesday. “We won’t rule anything out. This is a missing persons case, a search and rescue case.”
On Monday, the Placer County Sheriff’s Office flew a search helicopter over the area.
“Despite the numerous resources we have utilized, Kiely and her vehicle are still missing,” the sheriff’s office said. “We are currently coordinating with the California Highway Patrol, Truckee Police, FBI, and the Nevada County Sheriff’s Office as we continue our search for Kiely.”
Kiely’s mother, Lindsey Rodni-Nieman, said the wait has been grueling.
“My head is all over the place and I’m terrified. Bad thoughts are very strong and hard to keep at bay,” Rodni-Nieman told KCRA. “But I’m trying to hold out hope, you know, that we’ll find her, that she’ll come home.”
CNN’s Cheri Mossburg contributed to this report.