World Rugby has opened an investigation after referee Jaco Peyper appeared to mock Sebastien Vahaamahina in a photo with Wales fans.
Peyper, taking charge of his 50th Test, sent Vahaamahina off in Wales' dramatic Rugby World Cup triumph over Les Bleus on Sunday, with the lock dismissed for elbowing Aaron Wainwright.
Though head coaches Jacques Brunel and Warren Gatland backed Peyper's decision, the South African official is now at the centre of an investigation after he posed for a photo with a group of Wales supporters.
In the picture, which was circulated on social media, Peyper has his elbow raised into a fan's chin.
France Rugby Federation vice-president Serge Simon took to his official Twitter account to demand an explanation.
He posted: "This photo if it is true is shocking and explanations will be necessary."
World Rugby confirmed they are looking into the matter.
"World Rugby is aware of a picture on social media of referee Jaco Peyper with a group of Wales fans taken after last night's [Sunday's] quarter-final between Wales and France in Oita," the governing body said.
"It would be inappropriate to comment further while we are establishing the facts."