Family and friends of a 16-year-old Utah girl whose body was found in a shallow grave were awaiting the results of an autopsy and police investigation into her death.

Authorities announced Saturday that the body found last week in the shallow grave in a rural area north of Salt Lake City belonged to Alexis Rasmussen. She was last seen the night of Sept. 10, when she was babysitting for Eric and Dea Millerberg of North Ogden.

The couple has been arrested on unrelated charges, but neither has been named as suspects in Rasmussen's case. Police have declined to comment about the couple.

The girl's aunt, Tammy Reed, said police haven't told the family the cause of death or even whether detectives believe she was murdered.

"We're all saddened," she said. "We want to know why and how and who."

Rasmussen's mother had given her permission to stay at the Millerberg home that night because it was late. She was last heard from around 11:30 p.m. when she texted her mother saying the Millerbergs hadn't returned home. The couple said between 11 p.m. and midnight, she told them she was leaving to meet a friend at a local school, police said.

Family members have acknowledged that Rasmussen had run away before, and police previously said they were treating the investigation as a missing person case.

Police have said a tip from a confidential informant led them to an isolated area of Morgan County where the teen's remains were discovered.

Investigators were working to determine the cause of the girl's death, as well as who was responsible, North Ogden police spokesman Paul Rhoades said. He referred further queries about the case to Weber County Attorney Dee Smith.

"The circumstances surrounding her disappearance and the discovery of her body certainly suggest that we are dealing with a homicide," Smith told the The Salt Lake Tribune. "At the same time, we're real early into this for me to say with any confidence what took place."

Reed said her niece's untimely death is even more heartbreaking because she had a beautiful spirit and ebullient personality.

"Everything about Lexi was remarkable," she told the Deseret News. "(She touched people with) her heart, her smile, her eyes. She wanted to be a nurse. She had hopes and dreams and was always looking toward the future."