The IOC has told South Korean officials to bar a football player from collecting his bronze medal after he displayed a flag with a political message at the third-place match against Japan.
The International Olympic Committee says it has opened its own investigation into the incident during Friday's match.
The IOC says in a statement Saturday that "we have opened an inquiry and have asked the (South Korean Olympic committee) for an explanation."
The match in Cardiff, Wales, was seen as potentially raising diplomatic tensions between South Korea and Japan.
A South Korea flag with a slogan supporting sovereignty of disputed islands was reportedly displayed on the field.