Johannesburg - Police say the tragedy at the FNB Stadium in Soweto on Saturday afternoon when two people died in a stampede during the derby between Kaizer Chiefs and Orlando Pirates, happened when "a rolling mass of people were trying to get into the stadium."
Several people were injured as well.
"I can confirm the death of two people," police spokesperson Lorraine van Emmerik said.
She said several other people had also been injured when "a rolling mass of people were trying to get into the stadium" south of Johannesburg.
Sponsors Carling Black Label also confirmed "two fatalities caused by blunt force trauma".
They said one fan was critically injured and 16 other spectators suffered minor injuries.
The brewer said it was "saddened by the fatalities" from the crush caused by "a number of people who attempted to push through the stadium gates".
Match tickets were sold out two weeks before the game.
"This incident is extremely unfortunate as solid security plans were put in place," according to the Carling statement.
Police have launched an investigation into the crush.
Hlomla Hlangani, an intern video journalist at the SABC who was at the stadium, said the trouble occurred shortly after the match had started.
He said stadium security had to call in for police reinforcements after they were overpowered by a crowd of fans trying to rush through the gates.
He cited a witness who told him that 15 minutes into the match "there was lots of traffic to get inside the stadium... people were getting angry and some were drunk... and wanted to get into the stadium quickly".
South African Football Association (SAFA) said it was "deeply saddened by the tragedy".
"A football match is supposed to be a place of entertainment. What happened at FNB Stadium is very unfortunate," SAFA president Danny Jordaan, said in a statement.
The two worst football tragedies in South Africa involved matches between the same clubs - in 2001 when 43 people were killed, and in 1991, when the death toll was 42.
The worst football tragedy in the World occurred in 1964 in Lima during an Olympic qualifier between Peru and Argentina at the National Stadium. The official toll was 328 dead.