Divers searching for a missing 16-year-old girl said they found a car with a body inside it in a Northern California reservoir, not far from where she attended a huge party weeks ago. Authorities were working to confirm the identity, the sheriff’s office said.

Volunteer divers with a sonar-equipped group called Adventures with Purpose said they found Kiely Rodni of Truckee on Sunday inside her car, which they said came to rest upside down under about 14 feet of water in Prosser Reservoir, about 55 feet offshore.

The Nevada County Sheriff’s Office said in a social media post that it was notified that a car and body were found, but that the deceased person had not been identified. The office planned a news conference at 11 a.m. Monday.

Adventures with Purpose search members Doug Bishop and Nick Rinn briefly described the search in a Facebook livestream Monday morning. Rinn said they were limited in the scope of details they could release.

Bishop said they put two sonar boats in the water at 10:40 a.m. and by 11:15 a.m. Rinn detected an object with sonar technology. Bishop said he was able to confirm it was a vehicle. Rinn put on his gear and conducted the dive to examine the car.

“Once we confirmed it was indeed Kiely’s vehicle we immediately notified family, law enforcement and (the teen’s) dad and grandpa were on scene within minutes,” Bishop said.

Rodni was last seen Aug. 6 near the Prosser Family Campground in Truckee, attending a party with hundreds of young people, authorities have said. The campground is at the reservoir in the Sierra Nevada, about 165 miles northeast of San Francisco.

Her friend, Sami Smith was at the party with her and said Rodni had been planning to spend the night at the campground.

“I know that she wasn’t in the right mindset or state to drive. And if she were to have driven, she wouldn’t have made it far,” Smith told KOVR-TV.

Friends and family feared she had been kidnapped. Her phone had been out of service since the party, and her 2013 silver Honda CR-V had not been found.

Marine units from three local sheriff’s offices searched the reservoir. The search grew to a wide area of California and Nevada and involved at least 16 local, state and federal enforcement agencies. Dozens of family and friends also searched and offered a $50,000 reward.

Adventures with Purpose’s website says it has helped solve more than 20 missing person cold cases since 2019.

“We understand that the resource we provide with our unique skill set is rare and it is an honor to help agencies and families all across the nation,” Bishop said. “We will be working together with authorities here to share this knowledge over the next couple of days.”