Rattling every possible cage, investigators in the missing persons case of Nancy Guthrie are consulting with Walmart management and using "sniffers" to try to detect the unique signal of her pacemaker as they struggle to develop leads in the disappearance of Savannah Guthrie's mother.
Walmart comes into play because the suspect was wearing a backpack sold exclusively at Walmart. As for the sniffers, what they're using is a device to detect emissions from Guthrie's pacemaker as they sift through up to 50,000 leads that have come in to the FBI.
The high-tech tracking tool, known as a "signal sniffer," has been mounted on a helicopter to help pinpoint Guthrie's location. Signal sniffers are commonly utilized in missing person cases to detect low-power electronic signals like those emitted by a pacemaker.
Authorities are concerned about Nancy Guthrie's health due to her need for vital daily medicine, and the fact her pacemaker went offline when she left her house.
The suspect seen in the surveillance footage -- the one who presumably took her without her consent in the middle of the night -- is described as a man about 5 feet, 9 inches tall with a medium build.
He's wearing jeans and covering his face with a ski mask, and the only definitively identified clothing item is the 25-liter "Ozark Trail Hiker Pack" backpack, exclusive to Walmart, according to Pima County Sheriff Chris Nanos. Walmart is tracking sales of that item to help investigators.
In other developments, CBS reported a black glove found near Guthrie's home, which the FBI said "appears to match the gloves the subject in the surveillance video," has also undergone DNA testing. Federal authorities said they received the preliminary result of those tests on Saturday, and, once confirmed, the findings would be entered into the FBI's national database for DNA samples.
Investigators also officially ruled out any member of the Guthrie family as suspects, announcing the family had been cooperative. "I’m not going to sit in silence when others are attacking the innocent," Pima County Sheriff Chris Nanos told NBC News.
He also said claims that the case was a burglary gone wrong are false.
The FBI is offering a $100,000 reward for any information that leads to Guthrie or to the arrest of someone responsible for her disappearance. Anyone with information should call the FBI at 1-800-CALL-FBI or email http://tips.fbi.gov.