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A massive search effort was underway Tuesday morning for the missing California 16-year-old Kiely Rodni, who vanished after telling family she was going to head home from a high school graduation sendoff early Saturday.

The Placer County Sheriff’s Office has said they were investigating a possible abduction because the girl’s SUV was also unaccounted for. Rodni graduated from high school two years early, and it is unlike her to run away or fail to come home, according to her mother, Lindsey Rodni-Nieman.

A spokesperson told Fox News Digital on Tuesday that investigators were still "exploring all possibilities" and confirmed that teens were using alcohol and drugs at the party.

Rodni had enough drinks to become drunk, according to her friend and another recent graduate, Sami Smith, who added that she did not believe the teen would have driven under the circumstances.

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Kiely Rodni has blonde hair, hazel eyes and a nose ring

Kiely Rodni shown in two undated photos (findkiely.com)

"At the point when I left, I thought she was going to stay there," said Smith, who departed the campground just a few minutes before Rodni was last seen. "Everybody was camping. It was late enough that she should have stayed. She’s not the type to go and drunk drive or anything."

Smith said she spent most of the night with Rodni.

"For the amount of drinks we both had together, she’s not that dumb," she added. "I remember we were partying together. She was having fun. She seemed really happy — she was like normal, just on an adrenaline rush. Saying ‘Hi’ to everybody.

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Road sign in Search for Kiely Rodni

Search teams gather to investigate Kiely Rodni, who went missing on Aug. 6, 2022, after attending a party. (Derek Shook for Fox News Digital)

But Rodni-Nieman says her daughter texted her around 12:15 a.m. Saturday and said she was heading home. The family lives about 10 miles away from the campground at a lodge south of town.

Smith, 18, said that there were plenty of attendees whom she had not previously met but none who seemed suspicious, gave unwanted attention or followed the pair around.

She said she didn’t notice anyone much older and that the party consisted mainly of teens, recent graduates and some college students from the surrounding areas. Some came from as far away as San Francisco, she said, but that was not unusual because the area is a summer vacation town.

Search and rescue team is briefed on Kiely Rodni

Authorities brief a search-and-rescue team ahead of Tuesday morning's search for missing Kiely Rodni near Lake Tahoe. (Derek Shook for Fox News Digital)

"We met a few strangers together," she said. "We both tended to trust people. I say ‘tended to’ because now I don’t think I will continue to trust people. But she’ll give anyone the benefit of the doubt."

Search crews and police from multiple counties scoured through the area beginning early Tuesday morning.

They started by searching Lake Prosser by boat as the land-based search party gathered on the shoreline.

The search also included several aircraft, including helicopters and airplanes flying in formation above, and all-terrain vehicles, including four-wheelers, trikes and dirt bikes. There were search dogs present and at least 100 members of law enforcement visible, including members of the FBI, who initially focused their attention on Campsite 4.

Crews pulled the boats from the water around noon and FBI agents were seen knocking on doors in the area. The FBI did not immediately respond to a request for comment.

"Right now, we are currently searching many areas," said Angela Musallam, the Placer County Sheriff’s public information officer.

The party, which stretched from Friday night into Saturday morning at the Prosser Family Campground in the Tahoe National Forest, involved dozens or hundreds of kids from a handful of nearby communities in the rural area, including Truckee and North Lake.

Around 12:15 a.m., she texted her parents that she was heading home. However, according to her mother, no one has come forward to say they saw her leave, no one was with her at the time, and nobody could remember when she left or see her car drive away.

Her phone, which last pinged at the party, has been turned off. Authorities say her vehicle, a silver 2013 Honda CRV with the California license plate 8YUR127, is also unaccounted for.

Authorities are urging teens who were at the party to come forward, and the community announced a "Teen to Teen" information gathering event from 5 p.m. to 7:30 p.m. PT at the Tahoe City Save Mart in an effort to get attendees talking.

Boat Searches for Kiely Rodni

Search teams gather to investigate Kiely Rodni, who went missing on Aug. 6, 2022, after attending a party. (Derek Shook for Fox News Digital)

"We have had a lack of reach out from many Tahoe kids who were at the party or may know any information," the announcement reads. "We are only looking for information such as who was at the party that you may have seen [and] the times you came and left."

Rodni’s mother is asking anyone who attended the party and their parents to look through their photos, social media posts and videos for any signs of Rodni. Home and business owners in the surrounding area are also asked to check their surveillance cameras for signs of the girl on Aug. 5 and Aug. 6.

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Missing person banner for Kiely Rodni

Search teams gather to investigate Kiely Rodni, who went missing on Aug. 6, 2022, after attending a party. (Derek Shook for Fox News Digital)

Storefronts and signposts in the surrounding area and as far away as Reno have been plastered with missing-person flyers.

Rodni is described as 5 feet, 7 inches tall and around 118 pounds. She has blonde hair and hazel eyes. She has a tattoo on her ribs of the number "17."

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Kiely Rodni smiles at a picnic table

Kiely Rodni was last seen at a rural campground near the border of California and Nevada around 12:30 a.m., Saturday, according to local authorities. (Placer County Sheriff)

She was last seen wearing green Dickies pants, a black tank top and jewelry, according to authorities. She has a nose ring and several other piercings.

Anyone with information is asked to call the Placer County Sheriff’s Office’s dedicated tip line at 530-581-6320. Callers can remain anonymous.

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The California Highway Patrol is also urging anyone who sees Rodni to call 911.

The family is offering a $50,000 reward for Rodni's return, and Smith is asking members to share Rodni's story, raise awareness and call in any information that may help investigators.

She has also helped organize a website, findkiely.com, where friends and family are sharing the latest information they have gathered.

Fox News' Ashley Papa contributed to this report.