India, Aug. 2 -- Six months after Nancy Guthrie disappeared from her Tucson, Arizona home, Pima County Sheriff Chris Nanos explained on Saturday why authorities recently released two purported ransom notes.

"There are a number of pieces of information in these notes that just might jar someone to say, 'You know, I've heard that,' or the wording, the style of the writing," Nanos said in an interview-style video. It remains unclear if the notes were written by the same sender.

Nanos said investigators are still actively going through tens of thousands of tips, videos and forensic leads while searching for the 84-year-old mother of "Today" co-host Savannah Guthrie.

"It's very active," Nanos said. "We've got a lot of work ahead of us."

He...