Fifa says it is "looking into" a new video of Croatia defender Domagoj Vida in which he appears to again say "Glory to Ukraine!".
The video was posted online after the win against Russia that took Croatia into a semi-final against England.
The 29-year-old, who used to play for Dynamo Kiev, has already been warned by Fifa for a previous clip, which led to coach Ognjen Vukojevic being sent home by Croatia.
Fifa outlaws political statements.
Croatia play England in the World Cup semi-final on Wednesday (19:00 BST).
The first video drew criticism in Russia as the phrases used had previously been used by anti-Russian politicians in Ukraine.
Vida, who scored an extra-time goal against Russia and also converted a penalty in the shoot-out, later apologised.
In the second clip Vida can also be heard to say "Belgrade burn".
"Fifa is looking into the matter," said football's world governing body.
Earlier in the tournament Switzerland trio Granit Xhaka, Xherdan Shaqiri and Stephan Lichtsteiner were fined by Fifa for breaking rules over political celebrations in their match against Serbia.
Source: BBC NEWS