Supporters of the club have called the deaths political, due to the involvement of club supporters in Egypt's revolution in January 2011.
Eyewitness accounts say that supporters of the club were trapped in an alleyway as police fired teargas into the crowd.
This resulted in rioting, which led to police opening fire on the football fans.
On Monday Egypt's public prosecutor maintained the stampede caused a crush that led to some fans’ necks being broken. A spokesperson for Egypt's Forensic Authority blamed the fatalities on asphyxiation by teargas.
The Egyptian interior ministry claims that police clashed with Zamalek fans after a group called the Ultras White Knights attempted to enter the stadium without tickets.
The political affiliations of Egypt's Ultras have led fans to believe the deaths were revenge attacks by the police for the group's role in Egypt's 2011 uprising.
Zamalek player Omar Gaber was hailed by fans as a hero for refusing to play the match, while the club's management have threatened to suspend him.
The incident comes as the trial of the 2012 Port Said Massacre is ongoing.
Fans say that incident, in which 73 football fans were killed, is also connected to the political involvement of Egypt's Ultras.
Supporters have been barred from football games until recently due to fears of violence.
Egypt's Premier League has been suspended indefinitely following Sunday's incident.