A volunteer search group in Mexico launched an operation near the Arizona border after receiving an anonymous tip claiming that a "grave" connected to missing 84-year-old Nancy Guthrie had been found, but the search turned up empty, and the case remains unsolved four months after she vanished from her Tucson home.

The tip came in on a Wednesday, the Daily Mail reported, citing local Mexican outlet El Imparcial. Ramona Guadalupe Ayala Ortiz, who leads the Buscando Corazones collective in Nogales, said the tipster claimed Nancy had been buried in one of the streams in an area known as Mariposa, near the Mexico-Arizona border.

The group searched the location. Nancy was not found there.

A federal law enforcement source told Fox News that the "location was checked and Nancy was not found." The Pima County Sheriff's Office said it is aware of the reports but has not been contacted by Mexican authorities. The office added that "the investigation remains active and ongoing, and we will continue to follow up on credible information."

That statement offers little comfort to a family now deep into a nightmare with no resolution in sight, and to anyone paying attention, the lack of an arrest after four months raises hard questions about what investigators actually know and whether the trail has gone cold.

What happened to Nancy Guthrie

Nancy Guthrie, mother of Today Show host Savannah Guthrie, was last seen on the night of January 31 after being dropped off at her Tucson home following a family game night at her daughter Annie's house. She has not been seen since the early hours of February 1.

The circumstances suggest an abduction. Investigators have examined blood drops found on Nancy's front porch, a doorbell camera that had been torn down, gloves left at the scene, and surveillance footage from the area. No ransom was ever paid, despite what the Daily Mail described as blackmail messages received by the family. The family requested proof of life; none was provided.

About two dozen Pima County and FBI investigators are directing the ongoing case. In early April, FBI agents discovered what was described as "potentially critical" new DNA at Nancy's home. Sources told ABC News that agents sent the sample to a private Florida lab for testing. NewsNation previously reported that pieces of hair found inside Nancy's property are among the new evidence being examined.

Despite all of this activity, zero arrests have been made. Only a few people have been taken in for questioning.

A search group with grim experience

The Buscando Corazones collective is no stranger to what lies buried in the desert near the border. The group has previously discovered more than 25 unmarked graves in the Mariposa area alone, a detail that underscores the lawlessness of the terrain and the grim plausibility of the anonymous tip, even if this particular search came up empty.

That a civilian volunteer group in Mexico is now fielding tips about a missing American grandmother tells you something about the state of the investigation. It also tells you something about the border region itself, where unmarked graves accumulate and cross-border coordination between U.S. and Mexican law enforcement remains uneven at best.

A veteran investigator previously suggested Nancy Guthrie was likely targeted by someone local who knew the family, a theory that would point the case back toward Tucson rather than across the border. Whether the Mexico tip represents a genuine lead or a false trail remains an open question.

Sheriff Nanos steps back from the family

Adding a layer of unease to the case: Pima County Sheriff Chris Nanos revealed last month that he is no longer personally in contact with the Guthrie family. Asked directly whether he still communicates with them, Nanos told People magazine plainly:

"I personally am not. If they need the family for anything, they get in touch with them and the family. It works both ways."

That's a striking posture for the elected sheriff of the county where an 84-year-old woman was apparently taken from her own home. Direct contact with the family is now handled by detectives and the FBI, Nanos said. The sheriff did not elaborate on why the arrangement changed.

For a case this high-profile and this unsolved, the distance between the sheriff's office and the victim's family is worth noting. Families of crime victims deserve to feel that the people in charge are engaged, not delegating and drifting.

Savannah Guthrie's grief

Savannah Guthrie, 54, returned to Studio 1A in New York City to cohost the Today Show. But the weight of her mother's disappearance is visible. She tearfully told cohost Jenna Bush Hager on Monday:

"I cry every morning on the way to work."

A few days earlier, Guthrie shared a social media post revealing that she cries "every day" since her mother vanished four months ago. The post was a rare public window into what the family is enduring while investigators chase leads that so far have produced no arrest, no recovery, and no answers.

What remains unknown

The list of unanswered questions in this case is long and troubling. Who sent the blackmail messages to the family? What did the surveillance footage show before and after the doorbell camera was removed? What are the results, if any, of the DNA and hair testing now underway at the Florida lab? What evidence, if any, supported the anonymous tip before the Mexico search was launched?

Mexican authorities have not contacted the Pima County Sheriff's Office about the search, and the Daily Mail contacted the FBI for comment. The gap between the volume of evidence collected and the absence of any arrest is the central tension of this case.

Four months. Two dozen investigators. DNA, hair, blood, a torn-down camera, surveillance footage, blackmail messages, an anonymous tip pointing to a grave across the border, and still, nothing definitive.

Nancy Guthrie's family deserves more than an "active and ongoing" investigation. They deserve results. And the public deserves to know whether the people responsible for solving this case are any closer to doing so, or whether an 84-year-old woman simply vanished into a void that no one in authority can explain.