THORNTON, Colo. -- Police have arrested a 15-year-old boy in connection with the killing of a 10-year-old Thornton girl who went missing Wednesday while walking in her neighborhood and was later found dead not too far from where she was last seen.

The 15-year-old, who police are not identifying because he's a juvenile, was arrested late Saturday night for investigation of first-degree murder in the death of Kiaya Campbell, according to the Thornton Police Department.

Last night, Detectives arrested a 15-year-old male for investigation of first degree murder in the Kiaya Campbell case. #Kiaya pic.twitter.com/Y5weAXMqNv — Thornton Police Dept (@ThorntonPolice) June 11, 2017

Police said Campbell and a 15-year-old acquaintance were walking from her father's house to a shopping center near 136th Avenue and Colorado Boulevard around 7 p.m. Wednesday when the two apparently became separated in a rainstorm. The girl was last seen near 129th Avenue and Colorado Boulevard.

Thornton police spokesman Officer Victor Avila would not say whether the 15-year-old acquaintance Campbell was walking with is the teen who was arrested.

A day after the girl disappeared, 23 law enforcement agencies from across the state worked together by searching trails, open spaces and even bodies of water to find her. An AMBER Alert was also issued by the Colorado Bureau of Investigation and the police department even recruited public volunteers to help in the search.

Later that day, police called off the search, saying they had found a child's body approximately two miles from where 10-year-old was last seen.

By Friday afternoon, police confirmed the body they had found was Kiaya's, announcing they were investigating her death as a homicide. Without giving additional details, the Adams County Coroner explained the death was "other than accidental."

During the investigation, police said they collected a "large amount of evidence" -- approximately more than 100 pieces -- according to Denver7 reporter Liz Gelardi. That evidence is still being sorted out and will be analyzed by investigators.

Police evidence gloves also at home of Kiaya's dad. pic.twitter.com/rEvrQlXVyP — Liz Gelardi (@LizGelardi) June 10, 2017

On Saturday, three hours before people gathered to pay their respects to the girl, Thornton police cordoned off the area where the 10-year-old’s body was found. Police tweeted that they wanted to again check the area with trained search dogs.

The 15-year-old was arrested at around 11:38 p.m. Saturday and was booked into the Adams County Juvenile Facility, police said.

The investigation is still ongoing.

Anyone with information regarding this case is asked to call the Thornton Police tip line at (720) 977-5069.