Updated

A 6-year-old Utah girl was found dead in a canal Tuesday after her mother reported her missing from her bedroom.

Police say Sierra Newbold was sexually assaulted, murdered and left in the canal near her home in West Jordan, a suburb of Salt Lake City, Fox 13 reports.

The girl's grandfather tells The Associated Press the child's mother went into her bedroom at about 7:30 a.m. Tuesday morning and Sierra was gone.

"We don't have any idea how the girl disappeared or whether she was taken from the bedroom," Reed Newbold told The Associated Press. "It's a complete mystery."

Police say they found the child's body in the canal just 30 minutes after her mother reported her missing. An autopsy revealed she had been sexually assaulted and investigators officially ruled her death a homicide Wednesday.

Police Chief Doug Diamond says at this point investigators have no suspects, but believe the murder was an isolated incident.

He said that while residents in the area shouldn't panic, "there's obviously a predator out there."

"Our highest priority now is to identify, arrest, and successfully prosecute the person or persons responsible for this crime," Diamond said. "I share in the concern of our residents for the ongoing safety and security of our children."

Police say the child's parents are cooperating in the investigation, and Newbold says the parents are not suspects.

Police said there were no signs of a break-in at the family's home, but declined to provide further details of the investigation. 

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The Associated Press contributed to this report.