New Delhi, Feb. 12 -- The disappearance of 84-year-old Nancy Guthrie, mother of longtime "Today" show co-anchor Savannah Guthrie, has triggered an intense multi-agency investigation in Tucson, Arizona. The search for Nancy Guthrie has entered Day 12. Authorities believe she was abducted from her home in the early hours of February 1. Surveillance cameras captured a masked individual on her porch. With thousands of tips pouring in, ransom messages under review, and the FBI offering a reward, investigators are racing against time to determine what happened and bring her home safely.

As hundreds of detectives and federal agents continue working the case, authorities say thousands of tips are being reviewed.

Here's what we know so far.

Nan...