New Delhi, March 23 -- A week after it emerged that investigators in the Nancy Guthrie case were seeking footage from two specific dates: 11 January and 24 January, a new NBC report, citing Pima County Sheriff Chris Nanos, has now shed light on why those dates matter.

Nancy Guthrie, mother of Savannah Guthrie, co-host of NBC's Today show, has been missing since 1 February from her home in Tucson, Arizona. The search for the 84-year-old has now entered its eighth week, with authorities yet to find a major lead.

On 18 March, residents living near Guthrie's house told NBC that investigators had gone door-to-door, asking about particular dates. These included the weekend she disappeared and 11 January, a day roughly 20 days before officials...