Watch: Savannah Guthrie posts new video pleading to mother's kidnappers

US television presenter Savannah Guthrie has made another emotional plea to her mother Nancy's abductors in a video she posted on social media, asking them to share her mother's location.

"I'm asking you, begging you, to do the right thing now," she said. "Help us find her - tell us where to look for her."

Investigators believe that Nancy Guthrie, who was last seen on 31 January, was taken against her will from her home near Tucson, Arizona, but they have not shared a possible motive or arrested a suspect.

A ransom note that was sent in the days after the 84-year-old was abducted claimed she had died, according to investigators.

It was one of two ransom notes believed to be credible that were addressed to Nancy Guthrie's family and sent to news media shortly after her January kidnapping. The first demanded millions in Bitcoin for her release; the second stated that she had died, according to US media, which cited unnamed sources.

Why the trail went cold in Nancy Guthrie case

In her latest video posted on Monday, Savannah Guthrie addressed the possible kidnappers.

"It has been months since our mumwas taken from us," Guthrie said.

"Our family is in agony. We are in a nightmare that will not end. Nothing about our situation has changed. We have done our part, and we will never stop looking for her. We will always ache for her and feel that hole in our hearts."

She added: "Help us bring this situation to an end. For all of us, no matter where we've been and what we've done, I believe there is always a way home. Please make the right choice."

The Pima County Sheriff's Department has not commented on the contents of any apparent ransom notes, but the department said their investigation "remains active and ongoing".

The BBC's US partner, CBS News, and other news outlets reported that law enforcement had requested that media hold off publishing details of any of the notes while they investigated Nancy Guthrie's disappearance.

The FBI and Pima County have spent months investigating her mysterious abduction from her Arizona home.

Nancy Guthrie, who needs daily medication, vanished sometime after she was dropped off at her home by relatives on the January evening almost six months ago. She failed to show up the following morning at a friend's house to watch a virtual Sunday church service.

Earlier this year, authorities released images of a masked and armed suspect who covered the  front door camera at Nancy Guthrie's home before her disappearance.

An initial ransom note was sent the day after she went missing and demanded millions in Bitcoin for her release.

It gave specific details about her home, as well as details about her bedroom and the home's surroundings, investigators told CBS.

Savannah Guthrie has said some ransom notes sent to the family were believed to be fake. She has said that her mother may no longer be alive.

'Really feeling the love' - Savannah Guthrie returns to NBC as search for mother goes on

Ransom note claims Nancy Guthrie died after abduction