Guthrie search heads into third week

Law enforcement officials in the US have been gathering more potential evidence as the search for Nancy Guthrie heads into its third week.

Late Friday night, agents sealed off a road about 3.2 kilometres from Guthrie's home as part of their investigation.

The investigators also tagged and towed a Range Rover SUV from a nearby restaurant's parking lot.

Nancy Guthrie, mother of TV show host Savannah Guthrie, was reported missing on February 1.

Authorities said her blood was found on the front porch.

Doorbell video footage were made public showing a possible suspect, and purported ransom notes were sent to news outlets.