Desperate Arizona cops searching for Nancy Guthrie revealed they still have no suspect four days after the 84-year-old's disappearance as they brought in the FBI for help cracking the case they seem to be making little progress on. "We don't know if multiple people were involved," Pima County Sheriff Chris Nanos told a news conference Tuesday, as he again appealed for the public's help finding the missing mother of "Today" host Savannah Guthrie. He also responded, "no clue," when asked by a reporter where Nancy was, and how many people were involved in her disappearance.