FBI briefed on mysterious disappearance of Savannah Guthrie's mom — as cops say she couldn't 'move around' easily

The FBI has been briefed on the disappearance of "Today" show host Savannah Guthrie's mom in Arizona — as cops revealed the missing 84-year-old has physical ailments that limit her ability to move.

Authorities have been searching for Nancy Guthrie ever since she was reported missing in Tucson by her family over the weekend.

The feds have since been looped in on the search, NBC crime reporter Tom Winter told the "Today" show early Monday...