The search for TV host Savannah Guthrie’s mother, Nancy Guthrie, continued Tuesday morning. She is still missing after the deadline set by a ransom note from her kidnappers passed. The FBI has not found any suspects or persons of interest yet. The 84-year-old's family said on Sunday they would pay ransom to ensure her safe return. Authorities have not confirmed if the ransom note is real. Attempts to contact the kidnappers have failed. Officials said Monday night, "We are not aware of any continued communication between the Guthrie family and suspected kidnappers, nor have we identified a suspect or person of interest in this case at this time." The FBI is sending more agents from field offices across the US to Tucson, Arizona, where Nancy Guthrie lives. NBC News quoted the FBI: "We are currently operating a 24-hour command post that includes crisis management experts, analytic support, and investigative teams. But we still need the public’s help. Someone has that one piece of information that can help us bring Nancy home. We need that person to share what they know. Please call us at 1-800-CALL-FBI." In a video on social media Monday, Savannah Guthrie pleaded, "We are at an hour of desperation. And we need your help." Michael Rudzena, the family’s pastor, described Nancy as a "strong woman" and "fiercely loving." He said, "Prayer opens up possibilities in our own hearts. Leaving a door open for hope is a way to fight against that fatality." Authorities believe Nancy Guthrie was taken from her home on January 31 or early February 1. They have not verified if the ransom note sent to local press and TMZ is genuine. The Pima County sheriff said on Monday that no suspects, persons of interest, or related vehicles have been identified. They will hold a press conference if new developments occur. Investigators face challenges because Nancy’s smart doorbell was disconnected before her disappearance. Since she wasn’t subscribed to the service, there are no video images available, said Pima County Sheriff Chris Nanos.