TUCSON, Ariz. — Pima County Sheriff Chris Nanos dismissed the most recent alleged ransom communication in the Nancy Guthrie case as fraudulent, even as new details continue to surface in the nearly five-month search for the missing 84-year-old mother of "Today" co-anchor Savannah Guthrie.

After TMZ reported receiving an email from someone claiming to know the identities of those responsible for Guthrie's disappearance, Nanos addressed the letter's credibility during a June 26 appearance on Tucson radio station 1030 KVOI AM's "The Buckmaster Show."

"I think the FBI has done a number of arrests for false or fake ransom notes," Nanos told host Bill Buckmaster.

Nanos said he believed investigators were likely looking at another fraudulent submission, though he noted the FBI would continue its own review of the claim. The sheriff, whose department has worked alongside the FBI since Guthrie was reported missing in February, expressed frustration at how public attention surrounding the case has occasionally been exploited by people sending false information.

"It is a shame that these types of events occur," Nanos said. "People have great interest and that's good because it helps us but then it gets really abused."

The Pima County Sheriff's Department declined to comment further on the latest letter, citing the active nature of the investigation, and the FBI similarly declined to comment. The newest email arrives just days after NBC News reported that a second, separate note sent........

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