Today” show host Savannah Guthrie and her siblings made an emotional plea for the return of their mother, who remains missing days after police believe she was abducted from her home in Arizona.

“Everyone is looking for you, Mommy, everywhere,” Savannah Guthrie said in a video message posted on Wednesday alongside her sister and brother. “We will not rest. Your children will not rest until we are together again.”

The FBI is sending additional agents and experts to Pima County, Arizona, to help reinforce efforts on the ground and to aid local investigators in the case, sources told ABC News on Wednesday.

Among those being sent is a supervisor who will run a task force with experts in areas like hostage negotiation, data storage systems/networks and secure digital devices, the sources said.

Nancy Guthrie was last seen at her home near Tucson on Saturday night, according to the Pima County Sheriff’s Department.

Investigators do not believe Nancy Guthrie left her home willingly and said it appears she was abducted in her sleep early Sunday morning, the Pima County Sheriff’s Department told ABC News.

Nancy Guthrie’s family reported her missing on Sunday around noon local time, authorities said.

“We don’t know where she is,” Pima County Sheriff Chris Nanos said told reporters on Tuesday.

“We do believe that Nancy was taken from her home against her will, and that’s where we’re at,” he said.

The FBI is sending additional agents and experts to Pima County, Arizona, to help reinforce efforts on the ground and to aid local investigators in the case, sources told ABC News on Wednesday.

Among those being sent is a supervisor who will run a task force with experts in areas like hostage negotiation, data storage systems/networks and secure digital devices, the sources said.

Savannah Guthrie made an urgent plea for her mother’s return, citing the 84-year-old’s fragile health.

“Our mom is our heart and our home,” Savannah Guthrie said. “She is 84 years old, her health, her heart is fragile. She lives in constant pain. She is without any medicine. She needs it to survive. She needs it not to suffer.”

No suspect or person of interest has been identified in the case, the sheriff’s department said on Wednesday.

The sheriff’s department said it is reviewing possible ransom notes as part of the investigation. ABC Tucson affiliate KGUN said it received one of the letters, which it forwarded to law enforcement. Officials say they are investigating if any of these letters are legitimate.

Addressing reports of a ransom letter, Savannah Guthrie said Wednesday, “As a family, we are doing everything that we can. We are ready to talk. However, we live in a world where voices and images are easily manipulated. We need to know without a doubt that she is alive and that you have her. We want to hear from you and we are ready to listen. Please reach out to us.”

In a post on his social media platform on Wednesday night, President Donald Trump said he spoke with Savannah Guthrie and said he was “directing ALL Federal Law Enforcement to be at the family’s, and Local Law Enforcement’s, complete disposal, IMMEDIATELY.”

The post went on to say: “We are deploying all resources to get her mother home safely. The prayers of our Nation are with her and her family. GOD BLESS AND PROTECT NANCY!”

FBI Director Kash Patel was expected to be in Arizona to help oversee the investigation, according to multiple officials familiar with the matter. In addition to the FBI, an elite Border Patrol was helping with the investigation, according to multiple officials.

Nancy Guthrie was last seen at her home near Tucson on Saturday night, according to the Pima County Sheriff’s Department.

Investigators do not believe Nancy Guthrie left her home willingly and said it appears she was abducted in her sleep early Sunday morning, the Pima County Sheriff’s Department told ABC News.

Nancy Guthrie’s family reported her missing on Sunday around noon local time, authorities said.

“We don’t know where she is,” Pima County Sheriff Chris Nanos said told reporters on Tuesday.

“We do believe that Nancy was taken from her home against her will, and that’s where we’re at,” he said.