World Rugby said Monday it had launched an official investigation into the allegation that South Africa's Bongi Mbonambi directed a racial slur at Tom Curry of England during the Springboks' victory in the Rugby World Cup semi-final.
Mbonambi, 32, is alleged to have called England backrow forward Curry "you white (followed by an expletive)" in the first half of Saturday's 16-15 victory.
"World Rugby takes all allegations of discriminatory behaviour extremely seriously," the sport's governing body said in a statement on Monday, five days before South Africa face New Zealand in the World Cup final.
"We can confirm that we are formally reviewing the allegation made by England’s Tom Curry in relation to the use of discriminatory language during the England versus South Africa Rugby World Cup 2023 semi-final on Saturday.
"World Rugby will not be making further comment until the conclusion of the process."
Curry approached referee Ben O'Keeffe about half an hour into the hard-fought match in Paris to report the alleged comment and asked what he should do in response.
"Nothing, please. I'll be on it," replied O'Keeffe.
Curry was asked after the game whether Mbonambi, who also appeared to refuse to shake the England player's hand at the end of the match, had said something he had taken issue with.
"Yeah," replied the 25-year-old, before adding that "it does not need to be talked about".
South Africa Rugby said on Sunday they would look into the matter.
"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."
England coach Steve Borthwick declined to comment on the matter on Sunday.
Verbal abuse in rugby is rarely penalised, although England prop Joe Marler and South African Jacques Potgieter have been punished in the past.
Marler received a two match-ban for remarks addressed to Wales's Samson Lee in 2016 and Potgieter was fined for an on-field homophobic slur in a Super Rugby game in 2015.
The Springboks, though, will be nervously awaiting the outcome of World Rugby's investigation.
Mbonambi is the Springboks' only specialist hooker due to Malcom Marx's tournament-ending injury, although converted back row forward Deon Fourie has covered from the bench.
They can therefore ill afford to be without Mbonambi, who was man of the match in the quarter-final win over hosts France, for Saturday's final against fellow three-time champions New Zealand at the Stade de France.
All Blacks defence coach Scott McLeod acknowledged as such in a press conference on Monday.
"If anything came of that (World Rugby process) for them, I imagine that would be a massive dent for them," said McLeod.
"He is a leader of their team. When Siya (Kolisi) goes off, then he becomes captain. So I imagine that would really impact them."