Brett Guthrie

The neighbor of Nancy Guthrie recalled seeing a suspicious white van on their street before the 84-year-old grandmother disappeared from Arizona.

Brett McIntire, 72, reported the vehicle to police after noticing it lacked any company branding, unlike normal work vehicles, he told the New York Post.

'It was a white van, full-sized, with no printing on the sides. It was parked on the street,' he said.

He spotted the vehicle a few days before Nancy's disappearance and said that he answered some basic questions from police about the sighting.

But the experience shook McIntire, who now keeps a paper and pen with him during his neighborhood walks so he can report anything suspicious he might come across, he told The Post.

It also spooked his wife, Lisa, who is now considering buying security cameras for their home, despite having heavy metal doors.

'I’m kind of a deep sleeper,' she told The Post, despite acknowledging that they have a 'pretty secure residence'.

'It’s unlikely someone could get past one of the metal doors, but we’re a little concerned,' she said.

Nancy, who is the mother of Today Show host Savannah Guthrie, vanished from her $1 million home in Tucson last weekend.

Authorities think she was taken against her will as her doorbell camera was disconnected around 2am on Sunday.

Software data recorded movement at the home at 2.12am, which police acknowledge could have come from a person or animal.

Nancy did not have an active subscription with the doorbell app, so the company was unable to recover any footage.

Then at 2.28am, the app on her pacemaker was disconnected from her phone.

Nancy was reported missing shortly before noon Sunday after she didn't show up at a church.

While she is able to drive and her mind is sharp, the Pima County sheriff said she has difficulty walking even short distances.

She requires daily medicine vital to her health, has high blood pressure and heart issues, police have said.

It is now six days into the desperate search for the grandmother, but authorities have not identified any suspects or persons of interest.

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DNA tests showed blood found on Nancy's front porch was a match to her, Pima County Sheriff Chris Nanos said.

'Right now, we believe Nancy is still out there. We want her home,' Nanos said at a news conference earlier Thursday. He acknowledged, however, that authorities have no evidence she is unharmed.

Law enforcement is bringing more resources and people into the investigation, and the FBI announced Thursday it was offering up to $50,000 for information.

President Donald Trump said he has spoken with Guthrie and posted on social media that he was directing federal authorities to help where they can.

She has been off work since her mother's abduction and has dropped out of hosting NBC's coverage of the Milan Winter Olympics, which begins on Friday.

She joined her two siblings in an emotional plea on social media on Wednesday to say they're ready to talk to whoever sent the ransom notes.

'We need to know without a doubt that she is alive and that you have her. We want to hear from you and we are ready to listen. Please reach out to us,' she said while fighting off tears.

With her voice cracking, she addressed her mother directly, saying the family was praying for her and that people were looking for her. She was flanked by her brother Camron and their sister, Annie.

'Mamma, If you're listening, we need you to come home. We miss you,' Annie added.

The Daily Mail has contacted the Pima County Sheriff's Department for comment.