Nancy Guthrie's family cleared as possible suspects, with search in its third week

Police in Arizona say family members of Nancy Guthrie have been cleared as possible suspects, as speculation grows on social media about the whereabouts of the missing 84-year-old mother of NBC anchor Savannah Guthrie.

"The family has been nothing but co-operative and gracious and are victims in this case," said the Pima County Sheriff's Office, which has been leading the investigation.

"To suggest otherwise is not only wrong, it is cruel," the office said in a statement.

The Pima County Sheriff Chris Nanos told NBC News that his office sent out the statement because people had been "attacking the innocent".

Nanos told NBC in a text message that "kindness matters" and that it was "every cops duty to stand up and be that voice for our victims".

The search for Guthrie, who police say went missing on the early hours of 1 February, is now in its third week - and no suspects have been named.

Police have said Guthrie was taken from her home, and that blood was found on the floor of her porch. A video taken from a doorbell camera at Guthrie's residence has shown the man believed to have seized her. He wore a mask, gloves and backpack.

After conducting a forensic analysis of the video, the US Federal Bureau of Investigation (FBI) announced last week that it believed the man was between 5ft 9in and 5ft 10in (175-177cm) tall, with an average build.

They have also said they believe the suspect bought the mask and backpack at a Walmart and are contacting stores to find a list of people who made the purchases.

Officials have been reviewing surveillance footage from nearby Walmart locations, Nanos has said.

Investigators have also been testing a glove they found that seems to match the ones worn by the suspect.

They have created a DNA profile of an unknown male to put into a national FBI database, according to the BBC's US partner CBS News. That database could show a match if the suspect had a previous arrest and gave law enforcement a DNA sample in the past.

On Sunday, Savannah Guthrie, the Today show co-host, issued another video appeal to "whoever has her, or knows where she is". She added that Nancy Guthrie's loved ones "still have hope".

In the two weeks since Guthrie's disappearance, the FBI and local police have conducted a massive search operation involving helicopters, sniffer dogs and hundreds of officers, while taking in thousands of call-in tips.

On Friday, authorities executed a search warrant at a residence two miles from Guthrie's home but made no arrests.

Investigators are now employing new strategies to try to trace Guthrie. They are using a device that could detect signals coming from her pacemaker, law enforcement sources told CBS.

The sources said the tool, called a "signal sniffer", was mounted on a helicopter to fly over an area where officials believe she might be, to track down her exact location.

Guthrie was last seen on the evening of 31 January, when a family member dropped her off at her home following a get-together at her other daughter Annie Guthrie's house.

Members of her church noticed her absence the following day and notified her family.