Swiss prosecutors are investigating 53 possible money-laundering incidents involving the bidding process for the 2018 and 2022 FIFA World Cup tournaments.
Swiss attorney-general Michael Lauber said Wednesday that the transactions were reported by banks through Switzerland's anti-money laundering alert system.
Lauber said banks had done their duty in reporting the activity and warned that the case was "huge and complex."
He told reporters that he does not rule out interviewing FIFA President Sepp Blatter, who has agreed to step down in the wake of the scandal engulfing football's governing body.
The Swiss investigation has been looking into allegations of mismanagement and money laundering connected to the awarding of the 2018 and 2022 World Cups to Russia and Qatar, respectively.
A separate U.S. indictment issued last month charges nine FIFA officials and five corporate executives with offenses that include racketeering, wire fraud and money laundering.
2026 World Cup
FIFA has suspended the bidding process for the 2026 World Cup because of the ongoing controversy.
The host of the 2026 world football championship was set to be chosen by FIFA members during a 2017 meeting in Malaysia. It is not clear when the decision now will be made.
U.S. court records unsealed earlier this month show that a former executive committee member of FIFA admitted accepting bribes in connection with the 1998 and 2010 World Cups.
Charles Blazer, a U.S. citizen who spent two decades as one of the world's most powerful soccer officials, secretly pleaded guilty in November 2013 to 10 criminal counts in New York as part of an agreement with U.S. prosecutors, according to the partially redacted transcript of the hearing.
Blazer told a U.S. judge that he and others on FIFA's executive committee accepted bribes in connection with the choice of France as the host of the 1998 World Cup.
He said he also accepted bribes linked to the 2010 event awarded to South Africa.