Robbie Brady has 36 caps for Republic of Ireland
Fifa is "gathering evidence" into an alleged headbutt by the Republic of Ireland's Robbie Brady on Wales' Ashley Williams in their World Cup qualifier.
The incident occurred in the 61st minute of the Republic's 1-0 win in Cardiff on Monday, which put them into the World Cup qualifying play-offs.
If charged, Burnley's Brady could be a doubt for the play-offs, which will be played on 9-11 and 12-14 November.
The alleged, off the ball incident was not seen by referee Damir Skomina.
Brady had only just returned from a one-game ban for the Cardiff match.
"We are gathering evidence and cannot comment further," a Fifa spokesperson told BBC Sport.