Photos show door-to-door searches and desert sweeps in hunt for Nancy Guthrie

The search intensifies for missing Nancy Guthrie as FBI agents comb through rugged desert terrain and canvass a Tucson-area neighborhood. Hundreds of investigators are assigned to the case, which has captured national attention since the mother of “Today” show host Savannah Guthrie disappeared. Authorities say they believe she was taken against her will after being last seen at her home Jan. 31.