Nancy Guthrie’s family has offered a $1million reward(Image: WireImage)

A retired FBI agent believes investigators may already possess the identity of Nancy Guthrie’s abductor – though accessing that information presents a challenge at this stage. The 84 year old mother of NBC journalist Savannah Guthrie vanished over three weeks ago in a case that has captivated the nation.

Nancy was last observed close to her residence in the Catalina Foothills, outside Tucson, Arizona, on the evening of Saturday, January 31 after being dropped off by her son-in-law Tommaso Cioni. Authorities suspect she has been abducted.

The identity of the mother-of-three’s captor has apparently baffled investigators, but former FBI Special Agent Robin Dreeke believes those working the case might be nearer to a breakthrough than they realize. This development comes as the sheriff in the case issued an update stating he has a location theory he “believes” is true.

Appearing with Tony Brueski on his Hidden Killers podcast on YouTube, Robin suspects the FBI may have the potential suspect’s name “somewhere in a big plethora of stuff” – though they haven’t yet uncovered it.

The specialist was encouraged by reports that the FBI have presented dozens of names accompanied by photographs to a Tucson firearms dealer to determine if any individuals purchased a weapon within the past year, reports the Express US.

The search for Nancy Guthrie in Arizona continues(Image: Getty Images)

Although authorities didn’t achieve results through that specific lead, this demonstrates that law enforcement is advancing and the search may be narrowing, according to Robin. He explained: “I loved seeing this list that they have something. They have possibles. Now granted, our guy might not be on any of those possibles because if he didn’t have a cell phone or if he went to Walmart in somewhere else in the world you’re not going to have the pings.

“I’ve said this at the beginning – I think they have his name somewhere in a big plethora of stuff. They’ll eventually have enough to extract it from a couple of hundred names.”

The FBI has recently upped its reward for tips from $50,000 to $100,000, whilst Nancy’s relatives are putting up $1million for her safe return. Authorities are searching for a suspect described as standing between 5ft 9in and 5ft 10in tall with a medium build.

A retired FBI agent thinks investigators may already have the name of Nancy Guthrie’s kidnapper(Image: Nathan Congleton/NBC via Getty Images)

Video captured by a doorbell camera at Nancy’s residence shows a person dressed in a ski mask and gloves, also carrying a black 25-liter Ozark backpack.

Authorities have reportedly found DNA evidence at the location in what was characterized as a “mixed” sample.

Robin Dreeke, who brings 40 years of expertise to the table, believes this could be another promising development in the probe into Nancy’s disappearance.

He shared on the podcast: “The fact the DNA was mixed in the house is actually a good sign that it might have been the perpetrator. A lot of times normally it’s mixed when there’s a struggle of some sort. It’s taking some more time to separate it out from what I understand. That’s the one I would focus on.

“I remember when I was working 9/11 in New York, as ludicrous as some of the leads were we could not close the lead until we did the final interview of the person who brought it in. If the lead comes in you’ve got to close it out. And I’d be focusing, and I’m sure they are, in the DNA in the house.”