Savannah Guthrie's mother, Nancy Guthrie, missing in Arizona

The mother of "Today Show" host Savannah Guthrie is missing in Arizona.

Pima County Sheriff Chris Nanos told reporters Sunday evening that a family member called 911 around noon on Sunday to report that 84-year-old Nancy Guthrie was missing.

"We're here on "a search and rescue mission, we hope," Nanos said.

CBS Phoenix affiliate KPHO-TV reports that Nanos said Nancy Guthrie was last seen at her home in the Catalina Foothills area 9:30 p.m. Saturday.

According to KPHO, Nanos said there were "concerning circumstances" found at the home and that homicide detectives are also investigating.

He added that she's "not in good physical health" and that there's "grave concern" about her.

Nanos wouldn't rule out foul play but said the search and rescue mission is being conducted air and by ground.

A missing person poster from his office lists Nancy Guthrie as being five-feet-five inches tall and weighing 150 pounds.