Nanos added that authorities have uncovered new details about the final known moments before Guthrie's disappearance.
On the night of Jan. 31, Guthrie returned home around 9:48 p.m. Authorities said that within two minutes, the garage door closed, signaling the last sign that she was inside her home.
"That time, we assume that Nancy's home and probably going to bed," Nanos said.
Around 1:47 a.m. the following morning, Guthrie's doorbell camera disconnected, and its software detected a person on camera around 2:12 a.m. Officials said no video or playback subscription was available to confirm whether the detection was a person, or even an animal.
Roughly 40 minutes after the camera went offline, Guthrie's pacemaker also lost connection to her phone app, officials said.
The family then discovered Guthrie missing around 11:56 a.m. when she failed to show up for her regular church service.
Investigators confirmed that blood was found on the front porch and that DNA testing matched it to Guthrie. Nanos declined to confirm whether the suspected abduction was connected to forced entry, saying "we are not discussing that at all, whether it's forced entry or not."
Authorities are still awaiting additional forensic analysis, with more results expected.
Additionally, the FBI announced a $50,000 reward for information leading to Guthrie's recovery or the arrest of anyone involved in her disappearance.
The sheriff and the FBI emphasized that they are working closely together and have brought in additional law enforcement resources from the region to assist with the investigation. They are urging the public to come forward with any tips or information.
FBI Special Agent Keith Janke said authorities are taking the ransom note they received seriously, noting that one referenced an Apple Watch while another mentioned a floodlight. He added that he will refrain from going into further specifics.
Officials said the authors of the ransom note have reportedly not responded to the video released Wednesday by Savannah Guthrie and her siblings, and that the family is hoping to establish contact.
"The family is ready to talk, get proof of life because there has been no contact after that ransom note," Janke said.
He noted that the ransom note set an initial deadline of 5:00 p.m. Thursday and mentioned a second deadline for next Monday, following the initial cutoff.
"Any action taken on any ransom is ultimately decided by the family," Janke said.
When asked whether officials have communicated with the Mexican authorities, given Arizona’s status as a border state, the sheriff confirmed that they have not spoken with counterparts on the other side.
"I worked closely with the Mexican consulate, as are other consulates, being the sheriff, but no, I have not heard from them," Nanos said.
Janke urged those involved in the case to "do the right thing," calling on them to cooperate with authorities to bring Guthrie home safely.
"To anyone that may be involved. Do the right thing," Janke said. "This is an 84-year-old grandma. This is an 84-year-old grandma that needs vital medication for her well-being. You still have the time to do the right thing before this becomes a worse, much worse scenario for you. Please return Nancy home."