South Africa announced they will investigate allegations that one of their players used a racist slur against England's Tom Curry.
Curry drew the incident to the attention of referee Ben O'Keeffe in the second quarter of the match at the Stade de France.
Although the alleged slur is not audible on the ref mic, Curry's subsequent conversation with O'Keeffe is.
"Sir, if their hooker calls me a white c*** what do I do?" the Sale flanker said.
O'Keeffe replied: "Nothing, please. I'll be on it."
South Africa on Sunday responded by confirming they are looking into the incident.
"We are aware of the allegation, which we take very seriously, and are reviewing the available evidence. We will engage with Bongi [Mbonambi] if anything is found to substantiate the claim," an SA Rugby statement read.
When asked after the match if Mbonambi had said something he should not have done, Curry replied "yeah", although he declined to reveal the content of the remark.
Mbonambi, who took over as captain once Siya Kolisi had been replaced, refused to shake Curry's hand at the end of a dramatic clash in Paris that was won by Handre Pollard's penalty after 78 minutes.
World Rugby confirmed there is a 36-hour window from when the game ends for England to lodge a complaint to the citing officer, giving them until 10am BST on Monday to act.
The sport's global governing body can also choose to pursue the matter, with any case likely to be brought under the 'bringing the game into disrepute' banner.
Also, if the citing officer finds any evidence of the alleged racist remark, disciplinary proceedings can be triggered against Mbonambi, with an offence such as this likely to contravene law 9.12 – a player must not verbally abuse anyone.
England led for all but five minutes of the semi-final and were nine points ahead until RG Snyman went over in the 70th minute at a time when the Springboks' scrum was taking control through the introduction of the 'Bomb Squad'.
Jonny May said England's heroic effort against the world champions was fuelled by the belief that they had been dismissed as a serious threat by South Africa.
"I'll be honest, I don't think necessarily the South Africans respect us," May said.
"Some of the things their coach has openly said about us in their documentaries and stuff probably just adds fuel to the fire.
"We touched on their documentary and we've got staff who were with them and they gave us insight of how they feel about us."
