Rodni was last seen on Aug. 6 near the Prosser Family Campground in Truckee.
An autopsy has found that the body found in the Prosser Reservoir on Sunday is that of California teenager Kiely Rodni, the Placer County Sheriff's Office said.
"The Placer County Sheriff's Office and the Nevada County Sheriff's Office are in communication with Kiely's family and offer our deepest condolences to them during this extremely difficult time," the office wrote on Facebook. "This is an ongoing investigation, and no other information is available at this time."
California authorities believe that the body found in a vehicle submerged in a reservoir is that of missing teenager Kiely Rodni, the Nevada County Sheriff's Office said at a press conference Monday.
Earlier, authorities had confirmed the body was found in a vehicle that matches the description of the SUV that Rodni was driving, authorities told ABC News on Monday. The sheriff's office said it expects to have an official confirmation that the body belongs to Rodni soon.
The lake where the car was found was within the search radius, where law enforcement had been searching since the very beginning of the operation, and officials said they had searched the water previously.
The lake had been searched with sonar and divers, but the expertise and high-end equipment provided by Adventures With Purpose, an independent group that located the vehicle Sunday, allowed them to make the find.
Rodni, 16, was last seen on Aug. 6 around 12:30 a.m. local time near the Prosser Family Campground in the small town of Truckee, California, some 20 miles north of Lake Tahoe.
She was at a party with upward of 300 people when she vanished along with her vehicle, a silver 2013 Honda CRV with California license plates and a sticker of a ram below the rear wiper blade, according to the Placer County Sheriff's Office, which had led the search and investigation.
The vehicle, which was pulled from the water overnight, matches the description of Rodni's SUV, a spokesperson for the Nevada County Sheriff's Office, which is assisting in the investigation, confirmed to ABC News.
In a statement, the teen's family said they were "eternally grateful" for the love that friends, family, law enforcement, the media and communities all over the world showed them throughout their search for Rodni.
"We have weathered a storm of unfathomable force, and it is purely thanks to the army of warriors, matriarchs, healers and helpers holding us up that we continue to stand today," her family said. "Mr. Rogers famously told a story of 'looking for the helpers' whenever he saw scary things in the news. We have not had to look for the helpers, as you have all come to our rescue in full force. We are forever indebted to you."
The statement continued, "While we accept this sadness cast under death's shadow, the rising sun shines light upon us, reminding us not to mourn our loss, but to celebrate Kiely's spirit and the gift that we all received in knowing her. Kiely will surely remain with us even though we will not get her back."
Rodni's cellphone had been out of service since she went missing.
"Her cellphone went dead and became virtually untraceable shortly after," Angela Musallam, public information officer for the Placer County Sheriff's Office, told ABC News during an interview that aired Aug. 9 on "Good Morning America."
Last week, authorities said they were conducting sex offender compliance sweeps as part of their search for Rodni.
Rodni's mother, Lindsey Rodni-Nieman, told "Good Morning America during an interview" on Aug. 8 that the last text message she received from her daughter said she was planning to leave the party in about 45 minutes and would be coming "straight home."
Following her disappearance, Rodni was added to the FBI's missing persons database.
ABC News' Nadine El-Bawab, Marilyn Heck, Alex Stone and Morgan Winsor contributed to this report.