Law enforcement is giving an update on the Nancy Guthrie case.

Arizona's Pima County Sheriff Chris Nanos, in an interview with NBC News, revealed new developments in the case involving the disappearance of Guthrie, the mom of "Today" anchor Savannah Guthrie. While the sheriff "absolutely" believes they are getting closer to solving the case and are hopeful Guthrie is alive, NBC reported that a dedicated team from his homicide division is working with the FBI on the search.

One key clue in the case has been the backpack the suspect was wearing when he was captured on video outside Guthrie's home. The black, 25-liter "Ozark Trail Hiker Pack" backpack was identified as the private-label brand exclusively sold at Walmart. Authorities, experts say, could use that information to subpoena the retailer for a list of people who recently bought it in the greater Tucson, Arizona, area.

But Nanos said the suspect may have purchased it elsewhere. "We've now learned that maybe it wasn't purchased out of Walmart," he told NBC News correspondent Liz Kreutz. "That backpack new, is exclusive to Walmart, but who's to say I didn't buy it and put it on eBay? … That's what we're looking at."

Is Nancy Guthrie case close to being solved? These questions linger