(CNN) The remains of a 12-year-girl who disappeared in Weld County, Colorado, in 1984 have been recovered and identified, authorities said Thursday.

A work crew discovered the remains Tuesday while excavating for a pipeline, said Greeley Police Sgt. Joe Tymkowych. They are of Jonelle Matthews, based on evidence found at the scene and a coroner's examination, he told CNN.

Jonelle went missing on December 20, 1984, Tymkowych said. She would be 47 today had she survived.

She was last seen entering her home around 8 p.m. local time when she was dropped off by a friend and her friend's father after performing in a choir concert at school, according to a 2018 press release. When her parents returned home at 10 p.m., they found the front door open, and her shoes by a chair and her stockings thrown across the couch, CNN affiliate KDVR reported.

The press release says Greeley police renewed efforts to find Matthews and had assembled a new team of investigators to go through the evidence. The investigation remains active.

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