The hunt for Nancy Guthrie has suffered a major setback - more than 18 days after she disappeared.
A glove, found two miles from 84-year-old Nancy's Tuscon, Arizona, home, failed to match DNA found within her home.
Pima County Sheriff Chris Nanos offered no new leads as police failed to make a match in a national crime database.
The glove, found on Sunday, was thought to be the best piece of evidence in the ongoing search for breakfast show host Savannah Guthrie's mother.
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It appeared to visually match the one worn by a masked suspect on released Ring doorbell footage.
However, police said it had found additional DNA evidence which had not yet been analysed.
This marks the third week of the hunt, with no arrests or suspects named.
But a DNA expert has revealed her "biggest question" hanging over the case on its 18th day.
CeCe Moore said the glove was unlikely to identify a suspect, adding that it was too far from the crime scene.
She said: "My biggest question is, have they found DNA from an unknown male inside that house?"
The glove appeared to be a match to the one worn by the suspect in this video
| FBI VIA REUTERSThe FBI has confirmed they are now using investigative genetic genealogy (IGG) to search for suspects.
The forensic technique uses public genealogy databases to find potential relatives when traditional law enforcement databases produce no results.
Mrs Moore said "it is just a matter of time now" until a suspect is found using IGG.
Authorities have said they also found 16 gloves scattered near Nancy's home, most of which were found to belong to investigators on the scene.
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Nancy Guthrie (right), the mother of US Today show host Savannah (left), has now been missing for three weeks
| REUTERSThe sheriff said 400 investigators are continuing to analyse over 40,000 tips.
Authorities have also cleared the Guthrie family, naming them as victims of the case.
Nancy's son-in-law Tommaso Cioni faced unfounded online speculation that he was involved in the case.
Delivery driver Carlos Palazeulos was apprehended in Rio Rico, Arizona, around 60 miles from Nancy's Tuscon home in connection with the case, but was released without charge after several hours.
FBI agents process evidence from a grey Range Rover in connection with the case
|REUTERS
Answering questions from the press, he said he was not familiar with the case and he was only read his rights two hours after he was held.
Mr Nanos has dispelled claims the case has gone cold.
He said: "As long as we have the ability to chase a lead, it’s not cold.
"We're not going to give up. We're going to find Nancy, and we're going to find out who did this."