The Today show host and her family reported their 84-year-old mum missing at the end of January.
As the search for her continues, Guthrie's loved ones have issued a new statement and expressed their belief someone in her local community in Arizona might have information that could lead to her return.
The statement from Savannah, Annie, and Camron Guthrie and their spouses was shared during a KVOA News 4 Tucson special, Bring Her Home: The Disappearance of Nancy Guthrie, televised on Saturday.
"We are deeply grateful for the outpouring from neighbours, friends and the people of Tucson," it said.
"We are all family now. We continue to believe it is Tucsonans, and the greater southern Arizona community, that hold the key to finding resolution in this case. Someone knows something.
"It's possible a member of this community has information that they do not even realise is significant. We hope people search their memories, especially around the key timelines of January 31 and the early morning hours of February 1, as well as the late evening of January 11.
"We desperately ask this community for renewed attention to our mum's case - please consult camera footage, journal notes, text messages, observations or conversations that in retrospect may hold significance.
"No detail is too small. It may be the key."
The Pima County Sheriff's Department launched an urgent search for Nancy after she failed to show up for a church service on February 1, the day after her relatives had dropped her home.
Investigators believe she was kidnapped overnight, and have obtained surveillance footage of a masked man at her door.
Earlier in March, Pima County Sheriff Chris Nanos admitted investigators believed they knew the motive behind the kidnapping, but did not offer details.
"We believe we know why (the kidnapper) did this and we believe that it was targeted, but we're not 100 per cent sure of that," he told NBC News.
"I think day one, we had some strong beliefs about what happened, and those beliefs haven't diminished."
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