What to know about the investigation into Nancy Guthrie's disappearance and the search for clues

Law enforcement agents have been gathering more potential evidence as the search for “Today” show host Savannah Guthrie’s mother heads into its third week. Nancy Guthrie was last seen at her Arizona home on Jan. 31 and was reported missing the following day. Authorities say her blood was found on the front porch. Purported ransom notes were sent to news outlets, but two deadlines for paying have passed. Investigators are studying surveillance video, collecting DNA and sorting through tens of thousands of tips submitted by the public as they try to solve the mystery of her disappearance.