Around four surrounding buildings near the collapsed structure have been evacuated. Rescue teams are searching for other survivors trapped under the rubble, an official source said.
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 floor to the building without planning permission, and the second floor was undergoing renovation at the time of the collapse, Ahram online reported.
Both of 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.