South Africa tonight "raised their concerns" with match referee Roshan Mahanama over "allegations about the ball" while England were fielding on day three of the third Test.
Controversy broke out at Newlands after television cameras showed England seamer Stuart Broad stopping a straight drive during the morning session with the sole of his boot.
England were able to take only two wickets in 80 overs as South Africa piled up 312 and put the tourists in danger of losing a 1-0 series lead over the final two days of this penultimate Test.
But a South Africa spokesman said: "There have been several queries from the media about various video footage shown today, and certain allegations being made about the ball.
"We have raised our concerns with the match referee about it and we've left it to him to decide if any further action or investigation is necessary."
England team director Andy Flower attempted to play down the incident when interviewed at the end of the day's play.
"I don't think it is a big issue," he told Sky Sports. "It was a long, hot day and he put his foot out and stopped the ball. All he did was stop the ball."
Flower was more concerned about England's position after their most difficult day of the tour so far.
South Africa captain Graeme Smith will resume tomorrow unbeaten on 162.
He said: "It was a tough day for the boys, very hot. The wicket flattened out a little bit and there wasn't much movement for the seamers.
"But the South Africans played superbly today.
"The three seamers that were in the side toiled hard and (Graeme) Swann bowled well but without much luck."
Looking ahead to tomorrow, he added: "We have got to attack with the new ball. We have seen wickets fall early on all the days so far. We have definitely got to attack early.
"The first two days produced very difficult batting conditions, today was easier. We don't know what sort of conditions are going to arrive tomorrow. If it plays as easy as it has today, we have got a chance."