US television presenter Savannah Guthrie has spoken of her family's agony in the first interview since her mother's disappearance.


Nancy Guthrie, 84, has been missing since 1 February, when she was last seen at her Tucson, Arizona home. Police released images of a masked person captured by a security camera, but investigative leads received so far have fallen through.


To think of what she went through, I wake up every night in the middle of the night, every night, Guthrie said in an excerpt of the interview released by the TODAY show.


The Guthrie family is offering a $1 million reward, in addition to $100,000 pledged by the FBI, for information leading to Nancy's Guthrie's return.


Someone needs to do the right thing, Savannah Guthrie told her former TODAY show co-host Hoda Kotb in the emotional interview. We are in agony. It is unbearable.


Her family is one of 33 awaiting word from loved ones reported missing in Arizona in the past year to the US justice department's missing-persons database. Six of those went missing from Pima County, including Nancy Guthrie.


A tearful Savannah Guthrie described the debilitating agony that haunts her at night. In the darkness, I imagine her terror, she said.


And it is unthinkable - but those thoughts demand to be thought and I will not hide my face. But she needs to come home now.


Savannah Guthrie temporarily stepped away from her morning-show presenting duties after her mother's disappearance and was not part of NBC's coverage of the Winter Olympics as planned.


Kotb, her former co-presenter, has filled in on the morning show. After conducting the first interview, Kotb said there was a desperation and steeliness about Savannah, but that Savannah was hopeful that someone with relevant information about her mother's whereabouts would come forward.


The full interview, which will be released later this week, explores the police investigation, Savannah Guthrie's faith, and her joy despite the circumstances.


Pima County Sheriff Chris Nanos, leading the investigation, stated that authorities believe they have a motive and that Nancy Guthrie was targeted, although he declined to publicly reveal why, citing the ongoing investigation.


A nationwide search has yielded potential clues, including DNA evidence and ransom notes, but no suspect has been identified.


Nanos warned that the suspected kidnapper could carry out another abduction in the same area from which Guthrie was taken.


It'd be silly to tell people, 'Yeah, don't worry about it. You're not his target.' Don't think for a minute that because it happened to the Guthrie family, you're safe.


The Guthrie family donated $500,000 this month to the National Center for Missing & Exploited Children, saying they hope that the attention given to Nancy will help all families in need.