Voters in downtown Cairo's Qasr El-Nil have strongly backed the constitution.
17,958 voted "yes" and just 309 voted "no," Younis Fahmi Iskandar, head of the South Cairo election committee, announced on Thursday morning.
33,033 people were registered to vote in the constituency.
The referendum results for the rest of Cairo and north Sinai are yet to be announced.
Turnout in the 25 governorates already announced surpasses by around one million the turnout in the 2012 constitutional referendum.
Turnout Nationwide (25 governorates): 17,453,815
Yes: 16,821,944 (98%)
No: 336,675 (2%)