As the search continues for 84-year-old Nancy Guthrie in southern Arizona, authorities say there is no evidence she was taken across the U.S.–Mexico border, even as experts note that federal border protocols automatically come into play in disappearances near the international boundary.

Pima County Sheriff Chris Nanos told Fox News’ Jonathan Hunt that investigators have found no indication Guthrie was transported south of the border.

“You know, I’m sure the FBI has looked into that as well, but no,” Nanos said. “We check all the leads we have… we’re like everybody else. We know where Mexico is in relationship to this, and it’s a possibility. But no, we have nothing to indicate that.”

While the sheriff emphasized there is no evidence pointing to Mexico, retired FBI supervisory special agent Jason Pack says cross-border coordination is not dependent on confirmed proof.

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“When any disappearance occurs near the international border, certain federal protocols activate almost automatically, regardless of whether there’s confirmed evidence the victim crossed,” Pack told Fox News Digital.

According to Pack, the FBI maintains dedicated Border Liaison Agents stationed along the southern border who work directly with Mexican law enforcement counterparts in real time.

“That coordination happens at the working level, in real time, without waiting for a formal case to develop,” he explained.

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Those agents operate alongside the FBI’s Legal Attaché office in Mexico City, which serves as the bridge between FBI Headquarters, the U.S. Embassy, and Mexico’s federal attorney general’s office, he added. 

“These are not reactive positions,” Pack said. “They exist precisely so that when something like this happens, the relationships and channels are already in place.”

Pack stressed that Sheriff Nanos is being “accurate and responsible” in stating there is no indication Guthrie was taken into Mexico. However, he added a key investigative distinction.

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“From an investigative standpoint, the absence of evidence is not the same as evidence of absence,” Pack said. “Border protocols don’t require a confirmed lead. They require geographic proximity and a missing person. Both boxes are checked here.”

If cross-border movement were ever to become a credible line of inquiry, Pack said the formal mechanism for cooperation would be a Mutual Legal Assistance Treaty request, known as an MLAT.

“An MLAT allows U.S. authorities to formally request that Mexican authorities preserve evidence, conduct interviews, or share records,” he explained. That process runs through the Department of Justice’s Office of International Affairs and can move quickly “when there’s urgency and diplomatic goodwill — which currently exists between the two governments at the law enforcement level.”

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For now, authorities say there is no evidence Guthrie crossed into Mexico. Pack noted that established border coordination protocols are designed for cases occurring near the international boundary.

The search continues as investigators follow every available lead.

Nancy Guthrie disappearance timeline:

Jan. 31, 2026

Between 9:30–9:45 p.m. — Family drops Nancy off at home

9:50 p.m. — Garage door closes (per authorities)

Feb. 1, 2026

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1:47 a.m. — Doorbell camera disconnects

2:12 a.m. — Security camera detects motion

2:28 a.m. — Pacemaker disconnects from phone application

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11:56 a.m. — Family checks on Nancy after she misses weekly church livestream gathering

12:03 p.m. — 911 called

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12:15 p.m. — Sheriff’s deputies arrive at home

Fox News’ Jonathan Hunt and Greg Wehner contributed to this report. 

Stepheny Price covers crime, including missing persons, homicides and migrant crime. Send story tips to stepheny.price@fox.com.