FIFA has said there has been no evidence of match-fixing at any World Cup match and called on a German magazine which made allegations concerning Cameroon to offer proof.
Convicted match-fixer Wilson Raj Perumal has denied that he correctly predicted Cameroon's result against Croatia to Der Spiegel magazine before the game.
Der Spiegel is standing by its report but has yet to provide definitive evidence of the Facebook discussion with a journalist.
FIFA's head of media Delia Fischer told a news conference in Rio de Janeiro: "We have requested Der Spiegel to provide us with all the communications with Perumal and any other material in order to prove the allegations they have made.
"So far we have no evidence of any match manipulation on the betting market. The media and other stakeholders should not call people's or organisation's credibility into question just for headlines.
"It is really important to make sure that information is handled with the necessary respect and care."
Der Spiegel had claimed Perumal correctly predicted Cameroon would lose 4-0 against Croatia and a player would be sent off. Cameroon did indeed lose by that scoreline, with Alex Song dismissed in the first half.
Perumal, known as the Godfather of match-fixing, then issued a statement saying he made his remarks about Cameroon only after the match in question.
The contradictory statements will serve to further muddy the waters of the ethics investigation launched by the Cameroon football federation (FECAFOOT).
Perumal said in a statement: "Contrary to the 'revelations' published by the German weekly Der Spiegel that were picked up by news outlets worldwide, I did not predict the result of the Cameroon vs Croatia match.
"The Facebook chat with the Der Spiegel journalist took place a few days after the match - June 21st, as confirmed by my Facebook log - and was but an informal assessment of the behaviour of the Cameroon team at the Brazil 2014 World Cup after they had played two of their three group stage matches, including the one with Croatia.
"At no time did I make reference to four goals being scored or to a red card being issued."
Der Spiegel did not issue the definite proof of any conversation but responded by saying: "We firmly stand by our assertion that Mr Perumal wrote in a Facebook chat with der Spiegel some hours before the match Croatia vs Cameroon, that the result of the match will be a 4-0 victory for Croatia and that a player of Cameroon will get a red card in the first half."