The investigation into Nancy Guthrie’s disappearance has hit a roadblock as it stretches into its third week without significant progress.

Earlier this month, the 84-year-old mother of Savannah Guthrie, the Australian-born co-host of the US Today show, was reported missing.

Investigators suspect abduction and had pinned hopes on a glove, discovered in a field roughly three kilometers from her Tucson, Arizona home, to yield a crucial DNA match from the national database.

However, on Tuesday, the PIMA County Sheriff’s Department and the FBI announced that the glove did not match any existing DNA profiles.

As the search continues, here’s a summary of the situation so far.

When did Nancy Guthrie go missing?

Nancy Guthrie has become a familiar face to some viewers in the US due to her frequent appearances on the morning show with her daughter, Savannah, most recently in November.

The 84-year-old was last seen seen on 31 January when she was dropped off at her home near Tucson by her family after she had dined with them, and was reported missing by relatives the following day, authorities have said.

Sheriff Chris Nanos has said the Guthrie was extremely limited in her physical mobility and could not have left her home unassisted, leading investigators to conclude early on that she had been taken against her will.

Guthrie’s family have said she is in frail health and requires daily medication to survive. It’s unclear if Guthrie has had access to medication in the weeks since she disappeared.

Nanos told the Reuters news agency last week that no proof of life has surfaced since the abduction, but added that “there’s not been any proof of death either,” saying his working presumption is that Nancy Guthrie remains alive.

Authorities are treating her disappearance as an apparent kidnapping for ransom.

The FBI is offering a reward of up to US$100,000 ($142,000) for information leading to Guthrie’s location or the arrest of her captors.

Who are the suspects?

No one has publicly been named and authorities cleared her family on Monday, saying they had “been nothing but cooperative and gracious and are victims in this case”.

“To suggest otherwise is not only wrong, it is cruel. The Guthrie family are victims plain and simple…”

While no one has yet been identified, investigators have released several photographs and videos showing an individual wearing gloves, a mask and backpack approaching Guthrie’s doorstep in eerie black-and-white imagery.

A holstered gun is apparently visible on the person’s waist.

Nanos has said he believes the man, captured in video footage while trying to disable her doorbell camera in the early morning hours shortly before she was abducted, is the likely perpetrator and the primary suspect authorities are looking for.

The FBI believes the man is between 175-177cm tall with an average build.

The gloves found discarded in a field resembled those the man was wearing. While they didn’t return a DNA match, the sheriff’s department has said additional DNA evidence recovered at Guthrie’s residence was still being analysed.

Nanos on Tuesday did not say where in the home the DNA was found, but believed they may have some belonging to the suspect.

Last week, official said traces of blood found on Guthrie’s front porch were confirmed by DNA tests to have come from Guthrie.

How are authorities investigating Nancy Guthrie’s disappearance?

Much of the investigation has involved old-fashioned detective work, including investigators working with managers at outlets of US retail giant Walmart to pinpoint a person who purchased the backpack seen in the video, the sheriff’s office said.

Phillip Martin, co-owner of a Tucson gun store, told Reuters on Tuesday that an FBI agent who acknowledged he was working on the Guthrie case visited his shop with a list of fewer than 20 potential customers and asked if any had purchased a weapon there. Martin said he checked but none had.

The visit to this gun shop was more than a week ago, and law enforcement continue to refine lists of potential persons of interest. The list being shown to gun stores was developed from cross-referencing backpack and holster purchases and other data points, a law enforcement official told Reuters.

In other efforts, the sheriff’s department said investigators are working with a manufacturer and experts to try to locate Guthrie by detecting her heart pacemaker. News media reported that a “signal sniffer” device — chnology that produces a heat map to identify potential search targets within a given area — has been attached to low-flying aircraft.

The department said it is also still processing evidence from two search warrants executed last week. People detained for questioning had been released.

“As this investigation continues, you can expect to see similar activity,” the department said.

While not having “any evidence” to prove it, Nanos told the BBC he believes Guthrie is being held in the local area.

Purported ransom notes

At least two purported ransom notes have surfaced since she vanished, both of them delivered initially to news media outlets.

There has been no known direct contact between any suspects and Guthrie’s family or authorities.

Savannah Guthrie, 54, has posted several video messages, along with her brother Camron Guthrie and sister Annie Guthrie, pleading for their mother’s return and appealing for the public’s help in solving the case.

Over the weekend, she issued another plea to her mother’s captors.

“It’s never too late to do the right thing,” she said.

“We are here… And we believe in the essential goodness of every human being.”

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