The FBI is pulling back much of its Nancy Guthrie team from Tucson to the larger office in Phoenix, and the local sheriff is working to hand Nancy’s house back to her family for good — suggesting the investigation is entering a new phase.

(TUCSON, Ariz) -- Three-and-a-half weeks after Nancy Guthrie's abduction, the FBI is reducing its number of personnel in Tucson and relocating its command post to Phoenix, where it has its largest office in Arizona, sources briefed on the investigation told ABC News.

The FBI moved much of its command center for the Nancy Guthrie search from Tucson to Phoenix. Investigators continue to search the home, gather evidence, and follow new tips.

Nancy Guthrie, the mother of Today show host Savannah Guthrie, has now officially been missing for one month after she was last seen at her home on Jan. 31. As the search for the 84-year-old