For more than a decade, Savannah Guthrie has beamed into Americans' living rooms as the co-anchor of NBC's TODAY show, one of the highest-rating morning television programs in the country.So when her mother Nancy Guthrie went missing in January, her fame sparked a national obsession with the case and grabbed headlines around the world.Savannah Guthrie is a well-known media personality in the US. (AP: File)Despite the publicity and hundreds of sheriff's deputies, FBI agents and volunteers searching for the 84-year-old, Ms Guthrie has still not been found.It has been four months since she disappeared and several weeks since the release of eerie doorbell footage showing a masked person at her door.This is a timeline of events leading up to her alleged abduction and key moments from throughout the case.The community has thrown support behind the search for Nancy Guthrie. (Supplied: Reuters/Rebecca Noble)Saturday, January 315:32pm: Nancy Guthrie takes an Uber to her daughter Annie's home for dinner and a games night.9:48pm: She is driven home by her son-in-law, Tommaso Cioni.Mr Cioni watched from his car as Ms Guthrie walked to her garage and safely entered her house in the Catalina Foothills neighbourhood of Tucson, Arizona, police told the New York Times.This was the last time Ms Guthrie was seen.The home of Nancy Guthrie in Tucson, Arizona. (AP: Caitlin O'Hara)Sunday, February 11:47am: The doorbell camera at Ms Guthrie's home is disconnected.2:12am: The camera's software detects movement.Investigators initially said there was no video available because Ms Guthrie did not have an active monitoring subscription.But digital forensics experts kept working to find images in back-end software that might have been lost, corrupted or inaccessible.2:28am: Ms Guthrie's pacemaker app disconnects from her phone.The timeline of the hours leading up to Nancy Guthrie's disappearance released by local authorities. (ABC News Graphics: Lindsay Dunbar)11:56am: Her family checks on her after learning she did not attend church. Moments later, they call 911 to report her missing.12:15pm: Investigators arrive and launch a search operation, including the use of drones and dogs.Monday, February 2The Pima County Sheriff's Department provides its first news conference, announcing the investigation.Sheriff Chris Nanos said he believed Ms Guthrie was abducted and declared her home a "crime scene"."This is not dementia-related. She's as sharp as a tack," he said."The family wants everyone to know that this isn't someone who just wandered off."Sheriff Nanos raised concern that Ms Guthrie was reliant on daily medication and without it, "it can become fatal".Pima County Sheriff Chris Nanos provided regular updates on the case. (AP: Sejal Govindarao)Tucson's KOLD-TV reveals it received an email Monday night that appeared to be a ransom note.Tuesday, February 3A person familiar with the investigation told The Associated Press that investigators found signs of forced entry at Nancy Guthrie's home.Several of her personal items, including her mobile phone, wallet and car, were also still there after she disappeared.Donald Trump commented on the case, calling for the abductors to release Nancy Guthrie unharmed. (Reuters: Jonathan Ernst)President Donald Trump, speaking to reporters in the Oval Office, said he planned to get in touch with Savannah Guthrie and called the situation "terrible"."I always got along very good with Savannah," he said.Wednesday, February 4After allowing Ms Guthrie's family back on her property earlier in the week, authorities returned for a "follow-up investigation".That evening, Savannah Guthrie posted a video on social media, telling her mother's kidnapper that her family was ready to talk but they wanted proof she was alive."We need to know without a doubt that she is alive and that you have her," Savannah Guthrie said, reading from a prepared statement."We want to hear from you and we are ready to listen. Please reach out to us."At the end of the video, Savannah Guthrie addressed her mother directly, saying the family was praying for her and that people were looking for her."Mummy, if you are hearing this, you are a strong woman. You are God's precious daughter," she said.Thursday, February 5Officials reveal DNA testing determined blood found on the home's front porch was Nancy Guthrie's.The FBI offered a $US50,000 ($68,500) reward for information about Ms Guthrie's whereabouts.Friday, February 6Tucson TV station KOLD reports it received another email allegedly tied to the Guthrie case.The station did not disclose its contents and forwarded the message to investigators.Investigators return to Ms Guthrie's neighbourhood to gather more evidence.Investigators search Nancy Guthrie's property in the Catalina Foothills. (Reuters: Rebecca Noble)Saturday, February 7Savannah Guthrie posts another update to social media, indicating she would pay a ransom to secure the safe release of her mother."We received your message, and we understand. We beg you now to return our mother to us so that we can celebrate with her," she said."This is the only way we will have peace. This is very valuable to us, and we will pay."Monday, February 9Savannah Guthrie takes to social media again, pleading that her family was at an "hour of desperation".She asked for prayers and for people to report anything they might see or hear to law enforcement.Savannah Guthrie and her siblings take to social media with another plea to the abductors. (Instagram: savannahguthrie)An FBI spokesperson said the agency was not aware of ongoing communication between Nancy Guthrie's family and the possible kidnappers, despite a deadline set for that evening.Later, in a March interview, Savannah Guthrie clarified that some of the purported ransom notes were fake, but she believed the two she and her siblings responded to were real.Tuesday, February 10The FBI recovers doorbell camera footage of what it describes as an armed person tampering with a camera at Nancy Guthrie's front door.The footage was released, showing a person wearing a backpack and balaclava trying to cover the camera.Their gloved hand is then seen ripping out a plant from the front yard to block the camera's view.A security camera showed what the FBI described as someone tampering with the camera at Nancy Guthrie's front door. (Reuters: Pima County Sheriff's Department)Following the FBI's announcement, Savannah Guthrie posts images of the apparent kidnapper on Instagram."We believe she is still alive. Bring her home," she wrote, alongside phone numbers for the FBI and sheriff.The Pima County Sheriff's Department detains a man for questioning during a traffic stop south of Tucson, but he is later released.The sheriff's department said it also searched a location in Rio Rico, a city south of Tucson, with the help of the FBI.Wednesday, February 11FBI agents and sheriff's deputies knock on doors and comb the desert terrain in the neighbourhoods surrounding the homes of Nancy Guthrie and her oldest daughter, Annie Guthrie, whom she had visited hours before disappearing.The Pima County Sheriff's Department said several hundred detectives and agents had been assigned to the investigation.An investigator searches the area near Nancy Guthrie's home in the Catalina Foothills. ( Reuters: Rebecca Noble)Thursday, February 12Investigators ask residents in a 3.2-kilometre radius of Nancy Guthrie's home to share any camera footage and report any suspicious activity they noticed in the month before she disappeared.The FBI later doubles the reward to $US100,000 ($140,000) for information that would lead to Nancy Guthrie or an arrest and conviction.It also described the person seen in the video from Ms Guthrie's porch the night she went missing as a male with an average build who appeared to be about 175-centimetres tall.In the video, the FBI said he was wearing a black, 25-litre "Ozark Trail Hiker Pack" backpack.Images of a backpack were released to the public. (Supplied: FBI)Sunday, February 15The FBI finds a glove in a field about three kilometres from Ms Guthrie's home.It was sent for testing then submitted to the national DNA database, but it yielded no hits.Monday, February 16Pima County Sheriff's Department announces the Guthrie family, including all siblings and spouses, have been cleared as possible suspects.Wednesday, February 18Authorities again increase the reward, with Attorney Michael Hupy, the president of Milwaukee Crime Stoppers, saying a further $US100,000 would be offered for information about the disappearance.The FBI and Pima County Sheriff's Department deputies process evidence. (Reuters: Rebecca Noble)Sunday, March 22Savannah Guthrie posts a family statement on Instagram urging the public to think back to January 31, the night when her mother was last seen.She also specified the evening January 11."Please consult camera footage, journal notes, text messages, observations, or conversations that in retrospect may hold significance. No detail is too small," the statement said.The family also acknowledged that Ms Guthrie might not be alive.Savannah Guthrie poses alongside her mother Nancy during a production break in 2015. (Getty Images: Don Arnold/WireImage)NBC News correspondent Liz Kreutz reported on TODAY that she spoke with Sheriff Nanos about the significance of January 11.He said there was initial information provided by Google that a surveillance image of a masked man at Ms Guthrie's front door, recovered from a Nest camera at her home, was believed to be from January 11.Google later backed off that assertion, Sheriff Nanos was reported to have said.Pima County Sheriff Chris Nanos said they had been investigating footage believed to be from January 11. (Reuters: Rebecca Noble)Monday, March 26The Today show airs the first television interviews with Savannah Guthrie since her mother's disappearance."We are in agony," she told NBC News colleague Hoda Kotb, saying she woke up every night thinking about what her mother went through.She also shared new investigation details, including that the back doors at her mother's home were found propped open and her phone and purse were found inside.Savannah Guthrie embraces Carson Daly at the Today show. (Getty: Jose Perez/Bauer-Griffin/GC Images)Monday, April 6Savannah Guthrie returns to the Today show, which she has co-hosted since 2012."Here we go, ready or not," she said as the show went to air."Let's do the news." Savannah Guthrie returned to the Today show in April. (Getty: Jose Perez/Bauer-Griffin/GC Images)Friday, May 8Sheriff Nanos told Fox News Digital authorities were closer to solving the case, describing developments in the investigation as "really great".But he did not provide any further details.Tuesday, May 12Nancy Guthrie's disappearance hits a 100-day milestone.CBS news reported DNA collected from Ms Guthrie's home, which was first analysed at a private lab in Florida, had been shipped to an FBI crime lab in Quantico.The results were pending.Neighbours show support for the family, placing flowers outside Nancy Guthrie's home. (AP: Sejal Govindarao)Retired FBI Supervisory Special Agent Jason Pack said at this stage of an investigation, authorities would likely be re-interviewing witnesses and sorting through old tips and information with fresh eyes."A hundred days feels like forever to a family," he told CBS."In investigative terms, it can still be early."Wednesday, May 27Sheriff Nanos has repeatedly said the investigation was not considered cold.US news site Newsweek reported there had been no major breakthroughs, providing an update from the sheriff's department."This remains an active and ongoing investigation," a representative for the Pima County Sheriff's Department told Newsweek."Forensic analysis remains underway of video and DNA evidence. We have no additional information to provide at this time."ABC/AP