Ransom notes demanding millions of dollars for information about Nancy Guthrie's whereabouts may be legitimate, federal authorities conceded on Wednesday.

News outlets in Tucson, Arizona and TMZ received three ransom notes shortly after the 84-year-old mother of Today Show cohost Savannah Guthrie was abducted from her $1 million home in the Catalina Foothills on February 1.

The FBI has since determined that the three messages were fake, according to an unidentified official who spoke to Reuters on the condition of anonymity. 

But TMZ published an update the following day, claiming law enforcement sources refuted that report.

The bureau was then forced to clarify on Wednesday that while some of the ransom notes were determined to be 'extortion attempts without legitimacy,' others remain under investigation.

'The FBI and its task force partners have received several ransom notes over the course of this investigation,' the Phoenix FBI office posted to social media. 

'Some have been deemed to be extortion attempts without legitimacy. Other ransom demands may potentially be legitimate, and are still being investigated as such.'

The agency added that it is continuing to investigate Guthrie's disappearance 'as a kidnapping for ransom case.' 

The Pima County Sheriff's Department, which is leading the investigation, also released a statement on Wednesday, saying: 'Every tip and lead is taken seriously an is forwarded directly to our detectives who continue to work in coordination with the FBI.' 

The mother-of-three, in frail health with limited mobility, was last seen alive on January 31 at her home following a dinner with her daughter, Annie and son-in-law Tommaso Cioni, who dropped Guthrie back off at her home at around 9.50pm.

Hours later, at 1.47am, a masked individual wearing black latex gloves, a backpack and what seemed to be a holstered gun was captured outside Nancy's home disabling the doorbell camera.

Guthrie's pacemaker monitoring app disconnected from her home less than an hour later. Investigators now believe that could be the moment she was forcibly removed from the house. 

Her disappearance was reported the following day by family members after she failed to show up to a friend's house to watch a livestream of church services.

Drops of Guthrie's blood were found on the front porch of her home, and a review of her home showed she left behind essential items such as her wallet, cellphone, hearing aid and medication.

Three days after the shocking disappearance, TMZ had announced it received a ransom note just three days after Nancy went missing, demanding the Guthrie family fork over $4 million in Bitcoin for her return.

It said she was 'safe but scared,' and included details that had not yet been released to the public such as the floodlight in Nancy's backyard and what she was wearing at the time of her abduction.

The note concluded with a deadline for the ransom to be paid 'or else'.

But after federal agents decided to deposit just $152 into the specified cryptocurrency address, another ransom email was sent from the same IP address.

It said Guthrie had died and that her abductors 'never intended to hurt her,' 13 News reports.

The note also said Guthrie 'perished shortly after she was taken' is now 'buried in nature' and reiterates that the abductors 'are truly sorry.' 

It offered to deliver her body back to them in exchange for $4 million, Air Mail reported.

The following day, Savannah posted a heartbreaking clip on Instagram, sitting next to her brother, Camron, and sister, Annie.

'We beg you now to return our mother to us, so that we can celebrate with her,' the Today Show host pleaded in the video posted to her Instagram page.

'This is the only way we will have peace. This is very valuable to us, and we will pay.'

In the weeks since, TMZ's Harvey Levin said he has received even more messages, all of which he shared with the FBI.

In the most recent message he received from the same email address as the first two notes sent in February, Levin said the sender wrote that a video of Guthrie was on a cellphone in a secure place and that the sender once again demanded Bitcoin in exchange for information.

The FBI official quoted exclusively by Reuters on Tuesday said investigators had concluded the first two ransom notes originated from the same sender but were assessed as not credible, as was the third note reported by TMZ.

Pima County Sheriff Chris Nanos, who is leading the investigation, has also expressed skepticism about the legitimacy of all three ransom notes.

'I think the FBI has done a number of arrests for false or fake ransom notes,' he told Tucson radio station KVOI AM 1030's Buckmaster Show on June 26.

'It's a shame that that happens, but I think we're looking at another one of those today with what's been reported,' he said of the most recent letter TMZ received. 'But we'll let the FBI do their work.'

Federal agents have already arrested Derrick Callella for sending an 'imposter ransom demand' to family members.

He was charged with two counts of harassment by telecom devices for a fake ransom demand send by text message to Savannah Guthrie's sister and brother-in-law on Feb. 4.

Callella later pleaded not guilty, but a change-of-plea hearing in his case was set for Thursday in federal court in Tucson, court records show.

However, no suspects or persons of interest in Nancy's disappearance have been publicly named by the Pima County Sheriff's Department to date, five months after she vanished.  

'It is five months of agony and unending trauma for our family,' Savannah told 13 News. 'There is not a moment that goes by that we aren't actively trying to find our mom.

'We thank the people of Tucson for holding her in their hearts, as well as both the FBI and the Pima County Sheriff's Office for their tireless work on behalf of our family,' she continued, before pleading once again to 'Bring her home.'

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