With no sign of missing 84-year-old Nancy Guthrie, the search went underground in hopes of finding her over the weekend.

The search for Guthrie has entered Day 23 since the mother of “Today” host Savannah Guthrie was reported missing from her house in Tucson, Arizona, on Feb. 1.

Volunteer search crews spent the weekend in Tucson’s underground tunnels looking for Guthrie or any signs that could point to her whereabouts as authorities look for a break in the case.

A backpack was found in one of the search areas, leading the Pima County Sheriff’s Office to take it into evidence. The tunnels are in proximity to Guthrie’s home in the Catalina Foothills, approximately 8 miles northeast of downtown Tucson.

Guthrie suspect visited home twice

Nancy Guthrie suspectA suspect in the Nancy Guthrie disappearance outside her home on two separate occasions
Two photos obtained by NewsNation show the Nancy Guthrie suspect at her home on different days, sources confirm to Brian Entin and Libby Dean, indicating the suspect appears to have visited Guthrie’s house before the kidnapping.
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‘Mixed’ DNA causing delays

DNA pulled from Nancy Guthrie’s Tucson home is “mixed,” meaning samples have genetic material from more than one person, according to a report published Saturday.

Because of the intermingling, investigators are expected to have a more difficult time running the DNA through national databases to identify potential suspects, Pima County Sheriff Chris Nanos told NBC News.

The sheriff has added that it could take weeks, months, perhaps even a year for clarity.