Volunteers scour the desert for Nancy Guthrie

The disappearance of US Today host Savannah Guthrie’s mother three weeks ago inspired a small number of volunteers to launch their own search in the dense desert near her home in hopes of solving the case.

The Pima County Sheriff’s Department said it appreciates Nancy Guthrie’s concern but asks people who ask about volunteering to give investigators space to do their job.

“We all want to find Nancy, but it’s best left to the professionals,” the agency said in a statement over the weekend.

Nancy Guthrie, 84, was last seen at her home just outside Tucson on Jan. 31 and was reported missing the next day.

Authorities believe she was abducted, kidnapped or otherwise taken against her will. Drops of her blood were found on the front porch, but authorities have not released much evidence publicly.

Volunteers continued to search despite the Sheriff’s request that people not search on their own.

A small group reported finding a black backpack Sunday, but it was not the same brand as the backpack identified in video surveillance in which the FBI released a masked man at Guthrie’s home the night he disappeared.

A sheriff’s spokesman told Tucson television station KOLD that the bag and its contents did not appear to be valid clues.

Two women from the group Madres Buscadoras de Sonora, or “Searching Mothers of Sonora,” who carried digging tools outside Guthrie’s home on Sunday said they too would join the search.

They posted fliers with his picture and contact information in Guthrie’s mailbox.

Tony Estrada, a longtime former sheriff in neighboring Santa Cruz County, said volunteer searchers mean well to help and can serve as force multipliers, but it’s crucial their efforts are coordinated with law enforcement.

“You can’t have people everywhere looking for something and not reporting to anyone or letting them know that they’re going to be in that area,” Estrada said.

“They might be trampling on things that might be useful in the future.”