South Africa off-spinner Johan Botha has been reported for throwing during the third Test against Australia.
Umpires Billy Bowden and Aleem Dar, the TV umpire and match referee Chris Broad all collaborated in the report.
Broad said: "Concerns were raised by over the general legality of his bowling action and in particular his 'doosra' and quicker deliveries."
Botha can continue playing for South Africa but faces possible suspension if analysis confirms an illegal action.
The doosra, a delivery made famous by Sri Lankan star Muttiah Muralitharan, is a delivery that turns in the opposite direction to the conventional off-break.
Broad said the International Cricket Council would commission an immediate biomechanical report into Botha's action.
If Botha is found guilty and suspended, he would have to be re-assessed before bowling again in international cricket.
The 23-year-old made his Test debut in the match, taking a wicket in each innings in his side's eight-wicket defeat.
Captain Graeme Smith was questioned about Botha's unusual action at the post-match media conference but said he could see nothing wrong with it.
Botha will remain in the squad for thre one-day VB Series, with left-arm spinner Nicky Boje heading home.
Jacques Kallis passed tests on his elbow injury and will stay on at the expense of batsman AB de Villiers.
The South African team were fined by match referee Broad for a slow over rate on the final day of the Sydney Test, with the players fined 5% of their match fees and Smith 10%.
South Africa one-day squad: Graeme Smith (captain), Jacques Kallis, Johan Botha, Mark Boucher, Boeta Dippenaar, Herschelle Gibbs, Andrew Hall, Justin Kemp, Garnett Kruger, Charl Langeveldt, Andre Nel, Shaun Pollock, Ashwell Prince, Jaccques Rudolph, Monde Zondeki.