Savannah Guthrie's mother, Nancy Guthrie, missing in Arizona; sheriff calls her home a crime scene

The disappearance of "Today" show host Savannah Guthrie's mother, Nancy, is being treated as a crime, police said Monday, as they urged neighbors to review home video camera footage.

"We saw some things at the home that were concerning to us," Pima County Sheriff Chris Nanos told reporters Monday. "We believe now after we've processed that crime scene that we do in fact have a crime scene, that we do in fact have a crime, and we're asking the community's help."

Nancy Guthrie "is very limited in her mobility" and "we know she didn't just walk out of there," Nanos said, adding that there are other aspects at the scene which indicate she did not leave on her own.

She doesn't have any cognitive issues, but is in urgent need of her daily medication, authorities said.

Nanos didn't provide additional details about what investigators found concerning at the home, citing the ongoing investigation.

The FBI is assisting in the investigation, two sources told CBS News.

The search and rescue team worked through the night, employing drones, helicopters and heat sensors, but have since been sent home, Nanos said, as the search has turned to a criminal investigation. "Right now we don't see this as a search mission so much as we do a crime scene," he said.

Savannah Guthrie issued a statement on her mother's disappearance Monday.

"On behalf of our family, I want to thank everyone for the thoughts, prayers and messages of support," she said. "Right now, our focus remains on the safe return of our dear mom."

Guthrie urged anyone with information to contact the Pima County Sheriff's Department.

Nanos said Nancy Guthrie was last seen at her home in the Catalina Foothills area at 9:30 p.m. Saturday.