TUCSON, Ariz. – Sunday marks the eighth day of the search for 84-year-old Nancy Guthrie, a case that has shifted toward a high-stakes investigation as an alleged ransom deadline looms.

What’s New:

The Pima County Sheriff’s Department has maintained a constant presence at Guthrie’s home in the Catalina Foothills. Officials stated that deputies will remain on-site at the request of the family for security purposes.

The investigation saw increased activity earlier on Feb. 8 as authorities narrowed their focus on the property.

Video from the Fox Flight Team captured deputies searching a septic tank behind the home. Investigators were seen using a pole to inspect a manhole located at the rear of the property, though officials have not disclosed what they were looking for or if anything was recovered.

Local perspective:

Investigators keep returning to Nancy’s home, taping off the street, reopening it to the public, then sealing it off again. But the constant back and forth leaves neighbors questioning how the investigation is being handled.

“Why haven’t they closed it off the entire time? Because they’re opening it up. They should have shut if off a long time ago – in the beginning and kept it shut,” neighbor Dwayne Slate said.

Pima County deputies said the initial return was due to the FBI joining efforts.

“Monday morning quarterback, absolutely, I probably could have held off on that. We knew that the FBI, we’ve worked with them before in a lot of cases, and we felt like they could be of help in this with particularly the forensic analysis,” Sheriff Nanos said.

Neighbors concerned as deputies tape off Guthrie property several times

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After investigators taped off Nancy Guthrie’s Tucson-area home more than once amid the week-long investigation into her disappearance, neighbors are left concerned and want answers. FOX 10’s Megan Spector has the latest on the search efforts.

Dig deeper:

The tape went back up after there was a new message tied to an alleged ransom demand.

“It is not unusual for crime scenes to be released and then re-declared a crime scene,” retired FBI Special Agent Ken Gray said. But here’s the thing, is that that period of time in between that where it’s no longer a crime scene, somebody could go and then planted evidence or remove evidence. And so it makes it more difficult to when you find something new, to be introduced into an evidential case because you don’t have control of the crime scene throughout.”

But neighbors are still concerned and want answers, as they hope a lot more is goin gon behind the scenes that the public doesn’t know yet.

“We’re especially concerned that nothing has turned up yet,” neighbor Mike Hayes said. “That doesn’t mean there is really any lack of effort – it’s just not shared so we have virtually no knowledge of what’s really going on.”

“Law enforcement doesn’t always reveal all the details of where they stand in an investigation,” Gray added. They only reveal that which is necessary to obtain cooperation from the from the public… They are not going to just disclose facts or where they stand on the investigation because it jeopardizes the case.”

This Weekend:

The search follows an intense weekend of law enforcement activity. On the night of Feb. 7, investigators spent at least three hours at the home of Guthrie’s daughter, Annie Guthrie. Flashes were seen inside the residence as investigators appeared to take photographs, later emerging with several items.

The movement comes as a deadline spelled out in a purported ransom note is set for 5 p.m. Monday. The note, sent to a Tucson news station, allegedly demanded $6 million in Bitcoin. While authorities have not officially verified the credibility of the notes, at least one person has already been arrested for a separate “imposter” ransom demand earlier in the week.

In a third video posted to social media on Saturday evening, Savannah Guthrie, alongside her siblings Annie and Camron, spoke directly to potential captors.

“We received your message and we understand,” Savannah Guthrie said. “We beg you now to return our mother to us so we can celebrate with her. This is the only way we will have peace. This is very valuable to us and we will pay.”

The backstory:

Nancy Guthrie, who has a pacemaker and requires daily medication for heart issues, was last seen on Jan. 31. She was reported missing the next day after her family was notified that she hadn’t shown up for church.

Sheriff Chris Nanos released a timeline of the events in Guthrie’s disappearance.

What you can do:

Anyone with tips should contact the FBI at 1-800-CALL-FBI. A tipline was also created for the community to submit information. A reward of up to $50,000 is being offered for any information leading to Nancy Guthrie and/or the arrest and conviction of anyone involved.

Map of area where Nancy Guthrie was last seen.

The Source: The Pima County Sheriff’s Department and previous FOX 10 reports.