Around four surrounding buildings near the collapsed structure have been evacuated. Rescue teams were searching for other survivors trapped under the rubble, an official source said on Tuesday.
The collapse was caused by unauthorised construction of several extra stories on the old building.
A preliminary inspection of the site by prosecutors showed the owner had added two extra floors to the building without permission, and the second floor was undergoing renovation at the time of the collapse, Ahram online reported.
Building unauthorised floors caused the collapse, initial reports said
Both these factors could have contributed to the collapse, the report quoted prosecutors as saying.
Building collapses are common in Egypt due to illegal extensions and failure to adopt construction guidelines.