Suzanne Mubarak, 70, is expected to be taken to a Cairo prison, officials told The New York Times.
The deposed dictator is being held in a prison hospital where he is recovering from a heart attack, and the two Mubarak sons are in the Tora prison near Cairo along with other associates.
The state-owned newspaper al-Ahram's Web site said corruption investigator Khaled Selim went Friday to the Red Sea resort of Sharm el-Sheik where the Mubarak family retreated after the revolution to question Suzanne Mubarak.
She was formally detained only for 15 days for questioning but in Egypt that often spells indefinite imprisonment as the detention is routinely renewed. No charges have been filed against any members of the former ruling family.