The Pima County Sheriff's Department announced on Tuesday that investigators are now working directly with the manufacturer of Nancy Guthrie's pacemaker as they continue searching for the 84-year-old mother of "Today" show anchor Savannah Guthrie, who has been missing from her Tucson, Arizona, home since late January.
In a statement released on Feb. 17, the department said investigators "are attempting to locate the device and are working with the manufacturer and other experts in the field to assist in that effort." The update marks the latest step in an investigation that has stretched into its third week without any confirmed sighting of Nancy Guthrie.
Law enforcement sources previously told CBS News that a high-tech tracking tool known as a "signal sniffer" has been mounted on a helicopter in the Tucson desert to detect electronic signals that her pacemaker may emit, according to People.
The device was created by David Kennedy, a former NSA hacker, who told CNN that the helicopters must fly "really low to the ground" because the distance needed to ping a pacemaker signal is very short.
Tracy Walder, a former CIA and FBI agent, told People that the technology is "somewhat experimental" and requires the helicopter to be within roughly 30 to 100 feet of the pacemaker to pick up a signal.
A helicopter from the Pima County Sheriff's Department has been observed flying in a slow, grid-like pattern at low altitude near Guthrie's home in recent days, the New York Post reported.
Nancy Guthrie was last seen on the evening of Jan. 31, when her son-in-law dropped her off at her residence after a family dinner at approximately 9:48 p.m. Her garage door closed two minutes later. Authorities say a series of concerning events followed in the early morning hours of Feb. 1.
Her doorbell camera was disconnected at 1:47 a.m., and at 2:12 a.m., the camera briefly detected a person near her front door. The FBI has since released surveillance footage showing a masked individual wearing a handgun holster near the home. By 2:28 a.m., her pacemaker had disconnected from the monitoring app on her cellphone.
Guthrie has limited mobility and requires daily medication, and her daughter, Savannah, has described her health and heart as "fragile." She was reported missing on Feb. 1 when she failed to show up for church. No suspects or persons of interest have been publicly identified in the case, as per CBS News.
