Investigators are using a tracking device called “.signal finder“” that can detect signals emitted from electronic devices Nancy Guthrie This will continue into the third week.

David Kennedy, a former NSA hacker and inventor of the signal-detection device used in the investigation, told CBS News that Guthrie’s pacemaker was disconnected from an app on his phone, indicating the device had Bluetooth Low Energy technology, a power setting designed to keep the device running for several years.

Nancy Guthrie, 84-year-old mother of Today show co-host Savannah Guthriewas reported missing on February 1 after failing to show up for church after disappearing in the middle of the night from her home in Tucson, Arizona, in an apparent kidnapping. Authorities said Guthrie’s pacemaker was disconnected from his cell phone’s pacemaker app at 2:28 a.m.

Kennedy said Bluetooth Low Energy has a radius of only 10 to 15 feet, but with signal amplifiers and high-gain antennas, the radius can extend to hundreds of feet.

He said that after testing at home using a non-commercial drone and off-the-shelf items to modify it, he was able to extend the device’s detection range to about 800 feet.

“With the use of amplification, the use of drones and helicopters and other capabilities, we should be able to cover a much wider area and get within just a few meters of the actual signal itself,” Kennedy told CBS News.

The pacemaker sends out a Bluetooth signal every two to three minutes, allowing signal detectors to pick up its location, allowing law enforcement to view and track Nancy Guthrie’s location using her cell phone, Kennedy said.

The tracking tool was on board the helicopter Monday, a law enforcement official told CBS News. Sources said the helicopter with the equipment was flying slowly and low over the area where investigators were trying to find Guthrie.

President Kennedy said he believed the helicopter was used as a stopgap to get a rough idea of ​​what was happening in the area. He said signal-detecting equipment could be attached to drones or cars, but drones are more efficient because they can cover longer distances faster, and using helicopters or cars can cause signals to be obstructed by metal buildings or concrete walls.

Kennedy said authorities are not using large drone fleets because signal detection is considered an emerging capability for law enforcement, and it will take time to build the infrastructure for it. He said having about 50 to 60 drones covering 300 to 800 feet would speed up the process.

“It’s probably going to take a day or a few days or up to two weeks to cover a 120-foot-mile radius and be able to actually identify it, but overall it’s a pretty significant time savings,” Kennedy said. “In the end, it all comes down to the manpower, the drone operator.” [and] It’s just drone technology. ”