JOHANNESBURG, South Africa (AP) _ At least 40 people were killed Sunday and 50 injured when fans began brawling and touched off a panic among spectators at an exhibition soccer match, police and a witness said.

''The death toll is expected to rise as some of the more than 50 spectators injured are in a very serious condition,'' police Col. Johan Mostert told the independent South African Press Association. He said two children were among the dead.

Mostert and a photographer for the The Sowetan newspaper, Mbuzemi Zulu, said most of the deaths occurred when panicked spectators were crushed against a fence around the field and trampled by people fleeing the fighting.

Others were stabbed to death in the fighting in the stadium near Orkney, 80 miles southwest of Johannesburg. The match was an exhibition game between two clubs from the black township of Soweto.

''We saw cans and chairs flying. Then the game had to stop. There was chaos. Everyone was running for cover,'' Zulu said.

Zulu said about 40,000 spectators turned out for the match between the Kaizer Chiefs and the Orlando Pirates at Eugene Oppenheimer Stadium. Mostert said there were 20,000 spectators.

Supporters of both clubs sat together in the main grandstand, Zulu said. Zulu and Frans Phokwana, another witness, said Pirates' supporters appeared to have started the fighting after the Chiefs scored the first goal of the game.

''All hell broke loose about five minutes after the goal,'' Phokwana told SAPA. ''Kaizer Chiefs supporters tried to run away from the trouble.''

Mostert said there was no indication the violence was politically motivated, and that police were investigating the circumstances.

Phokwana said people sitting in the first few rows from the field were pushed into the fence and trampled.

''We thought it was a stampede,'' he said. ''People were lying all over the place. Some were unconscious; some were bleeding.''

African National Congress leader Nelson Mandela issued a statement Sunday night expressing condolences to the families of those killed. Mandela lives in Soweto, on the outskirts of Johannesburg.

Most spectators at the game were miners from the nearby Vaal Reef gold mine operated by the Anglo-American Corp., Zulu said.

Zulu described the fighting as fierce.

''They were stabbing each other,'' he said. ''People were using chairs and anything they could to protect themselves.''

The game stopped and the players were not involved in the fighting, Zulu said. He said ambulances had to struggle through crowds of people to reach the stadium, which later was secured by police.