On Friday evening, an extensive operation linked to the disappearance of 84-year-old Nancy Guthrie marked a major turning point in the Arizona investigation. According to a retired FBI agent, authorities are now swiftly moving to survey neighborhoods and expedite the analysis of crucial DNA evidence.

Following a promising lead, the Pima County SWAT team, in collaboration with the FBI, executed a federal search warrant at a residence near Tucson, approximately two miles from Guthrie’s home. During this operation, three individuals were taken into custody.

A fourth person was apprehended in connection with the warrant after being stopped by police in the parking lot of a Culver’s restaurant in Tucson. During this stop, a gray Range Rover was searched and subsequently towed away.

Jason Pack, a former FBI supervisory special agent with over 20 years of experience, informed Fox News Digital that these actions suggest agents were operating on precise, actionable intelligence.

A Pima County Sheriff’s deputy examines a Range Rover after a traffic stop in Tucson, Arizona, where one individual was detained as part of the investigation into Nancy Guthrie’s disappearance. (Photo by Kat Ramirez for Fox News Digital)

Nevertheless, Pack emphasized that the most challenging phase of the investigation is only beginning.

While the searches and interviews were ongoing Friday night, Pack said other teams of agents and analysts were likely already planning a full neighborhood canvas around the location that was searched.

“They’ll be going door to door, looking to talk face to face with neighbors,” Pack said. “They want to identify patterns of life for each of the people detained. … It will help corroborate or dispute whatever those who were detained are telling agents right now. If someone says ‘I wasn’t home that night,’ a neighbor’s Ring camera might tell a different story. Investigators are building the box.”

The Pima County Sheriff’s Department conducts a law enforcement operation at the intersection of Camino de Michael and East Orange Grove Road in Tucson, Ariz. (DWS for Fox News Digital)

Aside from canvassing the area, Pack said the most pressing concern is likely processing new evidence collected from at least two scenes Friday night.

“DNA that doesn’t belong to Nancy Guthrie or anyone close to her has already been identified at her property. Gloves have been recovered. Now you’ve got whatever was inside that Range Rover that warranted agents draping it with a tarp before the cameras could see,” he said. “All of that evidence needs to get to a lab.”

Pima County Sheriff Chris Nanos recently defended his department’s use of a private Florida lab to process evidence in the case, telling Fox News earlier this week the FBI agreed it was best to continue with the contracted business rather than transfer the evidence to the FBI’s comprehensive crime lab in Quantico, Virginia.

A man is detained following a traffic stop in Tucson, Ariz., Friday, in relation to the Nancy Guthrie disappearance case. (Kat Ramirez for Fox News Digital)

However, Pack stressed the situation is a race against the clock.

“Here’s the question. Do they wait until Monday to commercially ship it to a private lab? In past high-profile cases, I’ve seen FBI aircraft used to immediately shuttle evidence to the FBI Laboratory at Quantico,” he said. “That eliminates days of waiting. In a case involving a vulnerable 84-year-old woman who is without her heart medication, where every hour matters, you don’t wait for FedEx on Monday morning.”

Pack reiterated that in a time-sensitive case, authorities cannot afford to lose a weekend debating how to process evidence.

“That decision should have been made days ago. Which lab, which courier, what’s the turnaround,” he said. “If the FBI has the lead, Quantico is the logical answer, and I’d expect evidence to be wheels-up before the sun sets today.”

Authorities have not yet confirmed if the newly obtained evidence will be flown to the private lab or Quantico, or when it will take flight.