"It's moved from a search and rescue to a criminal investigation," Paul Sacco said.
Sacco's daughter, 23-year-old Aubrey Sacco, went missing while on a trek through the Asian country of Nepal. She had been hiking alone on a remote trail.
The Saccos organized a search from their Greeley home, but that search produced few results.
"There isn't a trace of evidence as to what happened," Sacco said.
Sacco and his son joined the search in Nepal and recently returned from that trip. They hiked the same trail his daughter was likely on and met people living around the area.
He says it is highly likely the villagers know what happened to his daughter, but are not talking for fear of retribution.
Still, Sacco says he has not lost hope.
"My daughter and I are particularly close," he said. "We're a lot alike in some ways and there's a certain intuition that I feel for her and I just honestly believe she's alive."
Sacco says because of Aubrey's disappearance, the U.S. Embassy is now advising women not to travel alone in Nepal.
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