Savannah Guthrie pleads for the public's help in the search for her missing mother

The FBI said Monday that it isn't aware of ongoing communication between Guthrie’s family and any suspected kidnappers more than a week after Nancy Guthrie went missing. The FBI has also not identified any suspects or persons of interest in Nancy Guthrie's disappearance, Connor Hagan, a spokesperson for the FBI, said in a statement. The agency is operating a 24-hour command post equipped with investigative teams and crisis management experts while asking for help from the public.

The family continues to believe Nancy Guthrie is out there and hearing everyone’s prayers, Savannah Guthrie said in the video released Monday.

“She was taken and we don’t know where, and we need your help,” Guthrie said in the video posted on Instagram, urging people nationwide to be on the lookout “no matter where you are, even if you’re far from Tucson, if you see anything, if you hear anything.”

The mysterious disappearance and search has riveted the country — from President Donald Trump, who spoke with Savannah Guthrie last week, to the online sleuths who’ve flooded social media with tips, theories and rumors.

The FBI is asking for the public’s help on digital billboards up in several major cities in Texas, California, Arizona and New Mexico. The FBI has offered a $50,000 reward for information.

Multiple news outlets received alleged ransom letters during the past week. At least one letter made monetary demands and set deadlines for receiving the money. The first passed last Thursday and a second one passed Monday evening.

Law enforcement officials declined to affirm that the letters were credible but said all tips were being investigated seriously. The Pima County Sheriff’s Department said Monday that law enforcement tip lines have received thousands of calls.

Authorities say they have growing concerns about Nancy Guthrie’s health because she needs daily medication. She is said to have a pacemaker and has dealt with high blood pressure and heart issues, according to sheriff’s dispatcher audio on broadcastify.com.

In a video Saturday, Savannah Guthrie said the family was prepared to pay for her mother’s return. “This is the only way we will have peace. This is very valuable to us, and we will pay.”

Authorities believe Nancy Guthrie was taken against her will from her home just outside Tucson. She was last seen there Jan. 31 and reported missing the next day after not attending church. DNA tests showed blood on Nancy Guthrie’s front porch was a match to her, and her doorbell camera was disconnected in the early hours of Sunday morning, Pima County Sheriff Chris Nanos has said.

Outside the home Monday, neighbors strolled by on their morning jogs and walks, while a county sheriff's deputy remained stationed out front.

Law enforcement's work at Guthrie homes will continue Tuesday “as part of the ongoing investigative process, including the expansion of the search and follow-up on new leads,” the Pima County Sheriff’s Department said in a statement Monday.

Detectives and agents carried out follow-up work in the neighborhood and other locations over the weekend as part of the investigation, the Pima County Sheriff’s Department said Sunday.

Investigators on Saturday were inside daughter Annie Guthrie’s home, about 4 miles (6 kilometers) from Nancy Guthrie's house. On Sunday, an investigator was seen using a pole to search an underground tank behind Nancy Guthrie’s home.