FIFA has asked a German magazine to provide details of all its conversations with convicted match-fixer Wilson Raj Perumal to prove its claim that a World Cup game could have been fixed.
FIFA director of security Ralf Mutschke said in a statement read out at a daily briefing in Rio de Janeiro on Wednesday that the allegations "put the integrity of FIFA World Cup matches in question, which is a serious allegation."
Der Spiegel reported that Perumal correctly predicted before the game that Cameroon would lose 4-0 to Croatia and have a player sent off in the first half.
Mutschke says FIFA has monitored all 56 World Cup games so far and has "no indication of any match manipulation on the betting market."
Perumal denied that he predicted details of the game.