Michael Lauber, the Swiss attorney general, says 53 "suspicious" banking relations are being looked into in a "complex" investigation.
The Swiss attorney general on Wednesday put no timeframe on dealing with a "huge and complex" criminal investigation into the award of the next two World Cups.
Michael Lauber revealed that nine terabytes of data had been seized by his office as they probe suspected irregularities in the bidding process for the 2018 World Cup in Russia and the tournament scheduled to take place in Qatar four years later.
He also revealed that 53 "suspicious" banking relations were being looked into and did not rule out interviewing FIFA president Sepp Blatter in a process which could take a considerable amount of time.
Lauber said in a statement: "Our investigation is of great complexity and quite substantial. To give you an example: The OAG [Office of the Attorney General] has seized around nine terabytes of data.
"So far, our investigative team obtained evidence concerning 104 banking relations; be aware that every banking relation represents several bank accounts."
He went on to reveal: "We note positively that banks in Switzerland did fulfil their duties to file suspicious activity reports.
"Partly in addition to the 104 banking relations already known to the authorities, banks announced 53 suspicious banking relations via the Anti-Money-Laundering-Framework of Switzerland.
"The procedure is huge and complex on many levels. I am well aware of that and will act accordingly."
Lauber also stated: "In concluding, we are faced with a complex investigation with many international implications. The prosecution is ongoing and will take time. It would not be professional to communicate at this moment a detailed timetable.
"The world of Football needs to be patient. By its nature, this investigation will take more than the legendary 90 minutes.
"Be assured: The OAG will give priority to this case and will act according to the principles of the rule of law. There will be formal interviews of all relevant people. By definition, this does not exclude interviewing the president of FIFA and / or its secretary general."
Blatter announced his intention to resign earlier this month after FIFA was thrown into chaos by allegations of corruption and the date of an election to appoint his successor is due to be set next month.
FIFA is in turmoil after nine past and present officials were indicted on charges of racketeering conspiracy and corruption last month.