TUCSON, Ariz. — Six months after 84-year-old Nancy Guthrie vanished from her home outside Tucson, the mother of "Today" show co-host Savannah Guthrie remains missing, with investigators still working through thousands of tips but no arrests and no confirmed suspects in a case authorities are treating as a kidnapping for ransom.

Guthrie disappeared in the early morning hours of Feb. 1 from her home in the Catalina Foothills area near Tucson. Her family has spent the past six months pleading publicly for information, even as the investigation has produced forensic evidence, surveillance footage and ransom notes without leading to her safe return.

Nancy Guthrie was last seen around 9:30 to 9:45 p.m. on Jan. 31, when family members dropped her off at her home after a visit. When she failed to appear for church the next morning, a fellow churchgoer alerted her family, who went to check on her around 11 a.m. and found her missing.

Pima County Sheriff Chris Nanos said early in the investigation that Guthrie had limited mobility and could not have left her home unaided, adding to the family's alarm given her dependence on daily medication. "She's 84, she needs her meds, her family needs her too," Nanos said at the time, urging the public to come forward with any information.

Authorities quickly determined that a crime had occurred. Nanos told reporters that Guthrie did........

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