The neighbourhood where Nancy Guthrie went missing has breathtaking views of the Santa Catalina mountains and strict limits on outdoor lighting to protect Tucson's standing as a stargazer's paradise.

The streets of the Catalina Foothills are lined with Arizona's iconic, giant three-armed Saguaro cacti – and throngs of journalists, investigators and neighbours fixated on the disappearance of the mother of TV presenter Savannah Guthrie.

"It's unbelievable. This just doesn't happen here," said Susan Crosson, who was out for an afternoon walk with her daughter Courtney and newborn grandson.

Crosson lives around the corner from Nancy Guthrie but does not know the family.

"We're shocked," she said. "We're locking our doors."

A security guard patrols the Guthrie house, keeping media and amateur sleuths from coming too close.

Outside the property a sign reads: "Dear Guthrie Family, your neighbors stand with you".

Laura Gargano, a neighbour and board member with a local group, the Catalina Foothills Association, admitted that some people in the area were beefing up their security since the 84-year-old disappeared.

Others are reviewing their security camera footage at the request of law enforcement.

But Gargano says the neighbourhood is peaceful and her cameras mostly capture coyotes and bobcats.

"I've just been very alarmed... not for my safety, to be honest, it's for Nancy," she said. "I just don't want to imagine what happened that night and what she might have felt at that moment."

Officers believe Nancy Guthrie was taken from her home against her will at around 02:30am local time on 1 February.

There were signs of a forced entry, a security camera had been removed and police found splatters of blood - which DNA tests have now confirmed belonged to Nancy Guthrie.

Police in Arizona have not yet identified a person of interest in the suspected abduction and continue to investigate a series of apparent ransom notes that may have been sent from the person or people behind the alleged crime.

While there's been an arrest surrounding a fake ransom note sent to the Guthrie family, police are taking other ransom communications seriously.

At least three media outlets said they have received ransom notes via email demanding bitcoin in exchange for Nancy's return.

According to news website TMZ, which reportedly received one of the letters, the kidnappers were demanding millions of dollars' worth of the cryptocurrency, which is popular with criminals and often difficult to trace.

Mary Coleman, a local news presenter for CBS News affiliate KOLD TV in Tucson, said the station had been sent one of the alleged ransom notes on Monday.

The station sent the letter to the authorities, who were trying to track down the senders. Coleman said the newsroom and law enforcement believe the letters sent to the media could be legitimate because they contained sensitive information about Nancy and the crime scene.

One note had two deadlines. One has since passed and another is on Monday, Coleman said. At the request of law enforcement, the media outlets have not disclosed all the demands in the letter.

"We love Nancy and we're praying for Nancy," said Ed Coates from St Andrew's Presbyterian Church, which Nancy has attended in the past. "It's heartbreaking for the whole community. She's very loved."

Nearby, St Philip's in the Hills Episcopal Church hosted a candlelight vigil for Nancy Guthrie, which many in the neighbourhood attended.

Savannah Guthrie is a household presence and many people feel like they know her as she's part of the fabric of their daily lives through her TV work. And it's easy for viewers to imagine, what if it was my mother?

Some wonder if outdoor lighting restrictions in the Catalina Foothills neighbourhood made it easier for Nancy Guthrie to be taken.

It is so incredibly dark here at night and lights are limited by law - they can only face downwards, which makes it all the more dazzling to look upwards at the stars in the sky.

When asked if the darkness could have played a part in Nancy Guthrie's disappearance, several local people disputed that theory, defending Tucson's rules against light pollution.

"Having lights can create glare, it doesn't always mean safety," said Courtney Crosson.

Down in the flats of Tucson away from the foothills and the throngs of media, people were talking about Nancy Guthrie's disappearance, but we didn't find many people too worried about security.

"I'm too poor to be kidnapped," said the woman checking us in to our hotel. "Nobody would come for me."