Australia’s Cameron Bancroft was spoken to by umpires about an object in his pocket while fielding during day three of the third Test against South Africa.
Television footage appeared to show Bancroft take a yellow object out of his pocket before shining the ball.
He was then shown putting the object down the front of his trousers before speaking to the on-field umpires Nigel Llong and Richard Illingworth.
Bancroft turned out his pockets, revealing a black cloth.
The umpires did not change the ball, and images of the incident on the big screen in Cape Town resulted in some booing from spectators.
The incident took place as South Africa built up a lead of more than 200 in their second innings against Australia.
This is the latest incident in a fractious four-match series in which several players have already been sanctioned by the International Cricket Council (ICC).
Earlier in the third Test, Australia opener David Warner was returning to the dressing room after being dismissed for 30 when he was confronted by a spectator.
The tourists’ coach Darren Lehmann later criticised the “disgraceful” verbal abuse directed at his players by the South African crowd, and Cricket Australia sent a letter of complaint to Cricket South Africa after the second day.
Following the first Test, Warner and South Africa’s Quinton de Kock were both charged by the ICC after an incident in a stairwell on the way back to the dressing rooms.
South African pace bowler Kagiso Rabada was banned for two matches after being found guilty of deliberately making contact with the tourists’ captain Steve Smith in the second Test, but successfully appealed against the decision.