Law enforcement activity is underway at a residence near Tucson's Orange Grove Road and First Avenue in connection with the disappearance of Nancy Guthrie, mother of NBC's Savannah Guthrie. The Pima County Sheriff's Department confirmed the investigation Friday night, noting it's a joint effort with the FBI that limits public disclosure.

Nancy Guthrie, 76, was reported missing on February 1, with authorities declaring her disappearance a crime the following day after finding concerning evidence at her home. The FBI has increased the reward to $100,000 for information leading to her location or the arrest of those responsible. Investigators are also examining a grey Range Rover found at a nearby Culver's restaurant.

Savannah Guthrie has made emotional appeals for public assistance, posting videos asking anyone with information to contact law enforcement. The case has driven significant viewership to the "Today" show, with ratings up 23% as audiences follow the developing story. An individual previously detained for questioning was released, and authorities continue to seek a male suspect described as 5'9" to 5'10" tall wearing a black backpack.