The sources told the media that 5,000 worshipers were in the church in the Imbaba neighbourhood of the Egyptian city, when the fire broke out, prompting a stampede.
According to official statements from the authorities and the church, the fire was caused by an electrical short circuit.
President Abdel Fattah al-Sisi expressed his condolences to the families of the victims.
Videos from the scene show a building engulfed in flames, with people trying to escape.