Two people were killed and several others injured as a result of a fan crush at the FNB Stadium in Soweto, Johannesburg.
The 87,000-seater stadium, the biggest in South Africa, was hosting the derby between Soweto rivals Orlando Pirates and Kaizer Chiefs, who won 1-0.
Michael Sun, the councillor for public safety in Johannesburg, confirmed the deaths on Twitter and said gates were opened to ensure crowd control. The match was allowed to finish.
"Situation report from FNB Soweto Derby: Stampede reported with multiple injuries, 2 confirmed fatal," Sun wrote.
"Soweto Derby update 2: All gates opened to ensure crowd control, game set to continue, ambulance capacity increased. Situation under control."
Jacques Grobbelaar, CEO of Stadium Management South Africa, told reporters: "We wish to express our condolences to the families of all those affected by the incident.
"This is extremely unfortunate as solid security plans were in place to ensure that this is a risk-free event.
"At kick-off, there was no reason to believe that the game needed to be delayed, given that the stadium was half full."
The stadium was rebuilt for the 2010 World Cup and hosted the final, where Spain beat Netherlands.