Police investigating the disappearance of a US TV host's mother are searching for a vehicle or vehicles that may be connected to her case.
Nancy Guthrie, whose daughter is NBC's Today show co-host Savannah Guthrie, is feared to have been kidnapped.
The 84-year-old was last seen at her own home near Tucson, Arizona, on the evening of Saturday 31 January, with a local TV station since receiving two messages that appear to be connected to the case.
One demanded money in exchange for her return and contained information about her Apple watch and floodlights on her property.
On Friday, a spokesperson for the convenience store chain Circle K told NBC News, Sky News's US partner, that officers visited one of their stores after "receiving a tip regarding a vehicle of interest, and our team has provided them access to the store's surveillance video".
Officials have not said whether the vehicle or vehicles are connected to any part of the disappearance.
It comes as the FBI and Pima County Sheriff's Department said they were aware of a "new message regarding Nancy Guthrie".
It was not clear what the message was or if it was connected to previously reported notes.
The message was sent to Tucson TV station KOLD, three officials briefed on the meeting told NBC News.
The FBI is working to confirm if it came from the same sender as the first reported ransom note, the sources said.
They stressed that the FBI has not yet verified if the first note came from someone who may have taken Ms Guthrie from her home.
Ms Guthrie's children have released two videos appealing to her apparent kidnappers.
On Wednesday, Savannah Guthrie posted a video in which she tearfully pleaded for her mother's safe return and appealed to the presumed kidnappers to open a line of communication with the family.
On Thursday evening, her son Cameron Guthrie said in a video posted to his sister's Instagram account: "Whoever is out there holding our mother, we want to hear from you."
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US President Donald Trump, speaking to reporters on Air Force One, said late on Friday that the investigation into Ms Guthrie's disappearance was going "very well".
"We have some clues that I think are very strong," he added. "We have some things that may be coming out reasonably soon."
US attorney general Pam Bondi told reporters earlier on Friday that federal authorities were assisting Arizona officials, but she declined to offer details.
"It breaks my heart for Savannah and for her family," she added.
Meanwhile, the sheriff investigating Ms Guthrie's disappearance said concern about her condition is growing because authorities say she needs daily medicine.
Pima County Sheriff Chris Nanos said: "Her conditions, I would imagine, are worsening day by day.
"She requires medication. And I have no way of knowing whether they're getting that medication to her."
Ms Guthrie was said to have a pacemaker and dealt with high blood pressure and heart issues, according to the sheriff's dispatcher audio on broadcastify.com.
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