The FBI is pulling back much of its Nancy Guthrie team from Tucson to the larger office in Phoenix, and the local sheriff is working to hand Nancy’s house back to her family for good — suggesting the investigation is entering a new phase.

While some agents will remain in Tucson, where the mother of “Today” show host Savannah Guthrie, 54, was abducted on Feb. 1, many investigators are returning to Phoenix to work on the case from there, sources with knowledge of the investigation told ABC News.

It’s been more than three and a half weeks since after the 84-year-old went missing, and there are still no suspects.

The shift does not necessarily mean that the agency is giving up the search for Nancy, or scaling back their investigation, former FBI Special Agent Tracy Walder told The Post.

Rather, the Phoenix office has the extra manpower to carry out the digital evidence work and analyze the DNA and tips received by the bureau, she explained.

“The FBI was probably taking agents from Phoenix down to Tucson. And they can’t be there indefinitely,” said Walder, who was previously stationed at the FBI’s Los Angeles Field Office.

“Clearly, the FBI has processed or gotten as much physical evidence as they need at the scene. So they don’t need agents there full-time,” she said, after agents were seen at Nancy’s property on Wednesday.

Drone footage showed detectives walking into her backyard by the pool and through a gate to the back patio.

Investigators were also seen standing at her front door, close to where blood was found on the ground.

With much of the case now analytical, the focus is now on poring over Walmart receipts, security footage, analyzing the mixed DNA sample taken from the house, and going through the roughly 1,500 new tips sent to the FBI since Nancy’s family offered up a $1 million reward on Tuesday.

The move comes as law enforcement prepares to return Nancy’s home to her family.

“I’m not at all surprised that they’re moving back. It doesn’t mean that they’ve abandoned the case at all,” said Walder, who previously criticized Pima County Sheriff’s Office for surrendering the crime scene so early.

“It’s no different from the Idaho murders; that house was eventually given back once the FBI was done processing it. In that situation, you were dealing with a resident agency as well, because Moscow, Idaho, is not large,” she said.

After an initial surge in the wake of Tuesday’s Instagram post announcing the reward, the number of calls to the Pima County Sheriff’s Office has tapered off, a source said.

The $1 million property in the Catalina Foothills neighborhood north of Tucson has been at the center of the investigation to find Nancy since she was reported missing on Feb. 1, hours after being dropped off at home by her son-in-law.

Nancy’s family has requested “No Trespassing” signs be put around the house to keep out snooping internet sleuths.