Toulon centre Mathieu Bastareaud has issued an apology after appearing to utter a "homophobic" insult at an opponent in Sunday's 36-0 European Champions Cup victory over Treviso.
Television footage appeared to show the France international calling Italian second row Sebastian Negri a "f******g f****t" after an altercation in the final minute of the match.
"I apologise for my reaction to insults from the Italian player. I reacted badly by responding to his provocation, I'm truly sorry for the people I might have hurt," Bastareaud wrote on his Twitter account.
In a statement on Sunday, competition organisers European Professional Club Rugby said they "had received a citing complaint against the RC Toulon player, Mathieu Bastareaud".It added: "Bastareaud is alleged to have verbally abused a Benetton Rugby player in the 80th minute of the match in contravention of Law 9.12.
"The complaint was made by the match citing commissioner, Dennis Jones."
Any suspension levied against Bastareaud would likely impact upon the 29-year-old's participation in the Six Nations, with France's opening game at home to Ireland on February 3.