Foul play is not suspected in the death of a Native American teenager whose body was found Monday morning about a mile from the highway rest stop near Billings, Montana, where she was last seen on New Year's Day, authorities said.

Selena Shelley Faye Not Afraid in an FBI photo. FBI

The girl, Selena Shelley Faye Not Afraid, 16, who lived on the Crow reservation near Billings with her mother, Jackie Big Hair, was last seen on New Year's Day at a rest area on Interstate 90 between Billings and Hardin. Witnesses said Selena was seen leaving a vehicle after returning from a party. The vehicle left the rest area, and when a relative arrived to pick Selena up, she was gone.

Big Horn County Sheriff Lawrence Big Hair said in a statement that a U.S. Interior Department team found the girl's body around 10:30 a.m. Monday during a systematic grid search southwest of the rest area.

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An autopsy will be conducted to determine the cause of death, but foul play is not suspected, the sheriff said.

Family, friends, members of the community and strangers had searched for Selena for nearly three weeks.

Cheryl Horn, Selena's aunt, was one of the hundreds of people who camped out at the rest area for days searching for answers in the girl's disappearance.

"We're not going to be just a file in the cabinet," Horn told "Dateline" last week. "We're going to find our girl. And when Selena is found, there are hundreds of more girls behind her waiting to be found."

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Many Native American women and girls have been reported missing in Montana and throughout the United States. In 2019, The Associated Press reported that nearly 300 cases of missing Native American women and girls were reported to law enforcement in Montana.

Horn told "Dateline" in an earlier interview that she would continue to be a voice for missing and murdered Native American women, even after Selena was found.

"A large percentage of these missing girls are indigenous," Cheryl said. "But this is not just an indigenous problem. This is a human problem. And right now, I have a voice. You have a voice. Those who are missing do not have a voice, and we need to be that voice for them."

After getting the news Monday, Horn posted to Facebook, saying: "We brought our baby girl home. Now she can Rest In Peace. Jackie and I want to thank everyone for helping us bring our girl home."

If you have any information about Selena's case, call the Big Horn County Sheriff's Office at (406) 665-9780 or the tip line at (406) 665-9800.