South Africa's Bongi Mbonambi has been accused of using a racial slur towards England flanker Tom Curry during his side's Rugby World Cup semi-final win.

"Nothing please," replied O'Keeffe.

England have 36 hours after the final whistle to refer such incidents to the citing commissioner, who could then call a disciplinary hearing.

With Saturday's match kicking off at 20:00 BST, the deadline for England to report back to World Rugby is on Monday morning.

Curry was asked after the match whether something untoward had been said to him by Mbonambi.

"Yeah," he replied, before adding that "it does not need to be talked about".

It appeared that Mbonambi refused to shake Curry's hand at the end of the match as the acrimony between the two sides continued after the final whistle.

SA Rugby - the South African rugby union - has started its own investigation into Curry's claim.

"We are aware of the allegation, which we take very seriously, and are reviewing the available evidence," it said.

"We will engage with Bongi if anything is found to substantiate the claim."

There is little precedent for sanctions around on-field verbal abuse, although England prop Joe Marler was banned for two games for a comment made to Wales' Samson Lee in 2016 and South African Jacques Potgieter was fined for an on-field homophobic slur in a Super Rugby game in 2015.

Mbonambi is the only specialist hooker in the South Africa squad after the Springbok management opted to replace the injured Malcolm Marx with fly-half Handre Pollard earlier in the tournament.

Deon Fourie, a converted back row, has been covering the position off the replacements bench.

The Springboks play New Zealand in next Saturday's Rugby World Cup final with both sides chasing a record fourth title.