Croatia's football federation says its leaders were not involved in suspected touting of World Cup final tickets.
Prosecutors in Zagreb asked police to investigate the illegal re-sale of tickets for Croatia's 4-2 loss against France in Moscow in July.
FIFA says it is "gathering information regarding the matter" and calls illicit sales "a serious issue."
The federation, whose president is 1998 World Cup striker Davor Suker, has promised to cooperate with the authorities.
It says there were "no indiscretions" by management and staff in handling and distributing a "relatively small number of tickets."
Though it is "theoretically possible that some individual violated FIFA's regulations and resold tickets," this was outside the federation's control.
The federation says the chance to buy them was "fairly distributed" among fans and "football family" members.