Article continues below advertisementThe search for Savannah Guthrie's missing mom is still unfolding - and now investigators are opening up about new hurdles in the case.Chris Nanos, sheriff of Pima County, shared an update as authorities continue looking for Nancy Guthrie. During an interview on Friday, February 20, he revealed that DNA collected from inside Nancy's home is "mixed," meaning it contains genetic material from more than one person. That detail, he explained, is making it harder to process through national databases.