The disappearance of Nancy Guthrie, the 84-year-old mother of NBC News anchor Savannah Guthrie, remains a mystery, with authorities continuing to investigate her suspected abduction.

On January 31, Nancy Guthrie vanished from her Tucson, Arizona, home in the middle of the night, prompting authorities to launch an investigation into her disappearance, which they believe may have been against her will.

As the investigation into Nancy Guthrie's disappearance continues, Arizona police are examining a series of ransom notes that may be linked to the case, but so far, no person of interest has been identified.

The Guthrie family has made public appeals for Nancy's safe return, requesting proof that she is still alive, as concerns for her well-being grow.

Here is a summary of the key facts in the case.

The last confirmed sighting of Nancy Guthrie was on the evening of January 31, when family members dropped her off at her home in the Catalina Foothills area of Tucson, around 21:30 local time (04:30 GMT).

A doorbell camera at her residence was disconnected and removed at 01:47 local time on February 1, and shortly after, at 02:28, the app connected to her pacemaker lost its connection to her phone.

The following day, church members noticed Nancy's absence at Sunday service and alerted her family, who then contacted the authorities.

After the family reported her missing, a search operation was launched, involving volunteers and federal officers from the Border Patrol, which continued into the next morning.

More than a week after her disappearance, officials released footage and images of a masked individual, reportedly armed, at Nancy Guthrie's doorstep on the night she vanished.

The footage shows the person approaching the front door, checking the camera, and then covering the lens with vegetation from the ground.

Savannah Guthrie shared the video on Instagram, urging anyone with information to come forward, saying, "Someone out there recognizes this person… We believe she is still out there. Bring her home."

Authorities have confirmed that blood found on Nancy Guthrie's porch belongs to her, raising concerns about her safety.

Officials have warned that Nancy Guthrie's health may be at risk due to her lack of medication.

According to Pima County Sheriff Chris Nanos, Nancy Guthrie is not in good physical health, but she does not have any reported cognitive issues.

As the investigation continues, the quiet Arizona suburb where Nancy Guthrie lives has been flooded with media crews, prompting authorities to restrict access to her street.

The FBI is reviewing a possible ransom note sent to several media outlets, which included details about an Apple watch and a floodlight at Nancy Guthrie's home.

One of the ransom notes sent to the media had two deadlines: 17:00 on February 5 and another on February 9.

The FBI arrested an individual for sending a fake ransom note on February 5.

On February 6, authorities announced that they were investigating a new message related to the case, stating that they were verifying the accuracy of the information provided.

The statement did not disclose who received the message or its contents.

A presenter for a local CBS News affiliate told the BBC that their channel had received the message, but did not provide further details.

In an emotional appeal, Savannah Guthrie addressed the potential abductor or abductors, saying, "We are ready to talk… We need to know without a doubt that she is alive and you have her… Please, reach out to us."

Savannah Guthrie's brother, Camron, also released a video on February 5, stating that the family had not received any contact from the person or people holding their mother.

In a separate video released on February 6, Savannah Guthrie said, "We received your message, and we understand. We beg you now to return our mother to us so that we can celebrate with her… And we will pay."

Ahead of a reported ransom deadline, Savannah Guthrie released another video on February 6, pleading for the public's help in locating her missing mother.

In the video posted on Instagram, she said, "I just want to share a few thoughts as we enter another week of this nightmare… She was taken, and we don't know where. And we need your help."

On February 6, officials announced a reward of $50,000 (£36,000) for information leading to an arrest in the case.

US President Donald Trump has described the case as "very unusual" and has ordered federal authorities to assist in the investigation.

Savannah Guthrie, 54, is a prominent American broadcast journalist who has co-anchored NBC News' Today since 2012 and serves as the network's chief legal correspondent.

Born in Australia, Savannah Guthrie moved to Tucson, Arizona, with her family at a young age and spent most of her childhood there.

In 2015, she visited Australia with her mother, Nancy, fulfilling a "lifelong dream to return" and recreating happy memories from her childhood.

Savannah Guthrie has maintained a neutral stance in her reporting, interviewing prominent figures such as presidents Barack Obama, Joe Biden, and Donald Trump.

She holds a law degree from Georgetown University and a bachelor's degree in journalism from the University of Arizona.

Throughout her career, Savannah Guthrie has won numerous awards, including an Edward R Murrow Award and multiple News Emmys, recognizing her excellence in journalism.

One of her notable interviews was with Donald Trump, which took place a month before the 2020 election.

Savannah Guthrie's professional background and experience have equipped her to navigate complex stories and high-pressure situations.

Her personal connection to the case, however, has made the investigation into her mother's disappearance a deeply emotional and challenging experience.

As the search for Nancy Guthrie continues, the family and authorities remain hopeful that she will be found safe and returned home soon.