Swiss investigators are examining 53 possible cases of money laundering and 104 incidents of suspicious activity in Swiss bank accounts as part of their investigation into the awarding of the 2018 and 2022 World Cups.

The Swiss attorney general Michael Lauber said investigators were examining “nine terabytes” of data from Fifa’s Zurich headquarters and Swiss banks.

“I am well aware of the enormous public interest in our investigation. Equally enormous is the public interest in an independent criminal procedure,” Lauber said.

“Our investigation is of great complexity and quite substantial. To give you an example: The SAG [Swiss attorney general’s office] has seized around nine terabytes of data. So far, our investigative team has obtained evidence concerning 104 banking relations; be aware that every banking relation represents several bank accounts.”

He warned there would be interviews of “all relevant people” including the Fifa president Sepp Blatter, who promised to step down in the wake of the US indictment, and the general secretary, Jérôme Valcke, who is under pressure to explain how much he knew about a $10m payment from South Africa to the Caribbean that US prosecutors claimed was a bribe.

News of the Swiss investigation into the controversial World Cup bidding process emerged on the same day that US prosecutors alleged a “World Cup of fraud” stretching back over two decades.

Fifa argued that the Swiss investigation was as a result of it handing over documents relating to an investigation by its ethics committee chief, Michael Garcia, and that as such it was in fact the “injured party”. However, the scope of Lauber’s investigation has since expanded.

“For the time being Fifa is the injured party, that is true. They filed the report and this is the actual status as we conduct investigations against unknown persons,” said Lauber, but he said that could change.

“We didn’t start the investigation against Fifa. We started the investigations based on that [report] and based on a mutual legal assistance request from the US.”

Lauber said he was working to his own schedule and was not concerned about “collateral damage” elsewhere.

“We are faced with a complex investigation with many international implications. The prosecution is ongoing and will take time,” he said. “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.”

Lauber, who said the “huge and complex” investigation could take months if not years to complete.

The head of Fifa’s audit and compliance committee, Domenico Scala, said last week in the wake of Blatter’s promise to step down as Fifa president, that a revote on the 2018 and 2022 tournaments could not be ruled out.

“If evidence should emerge that the awards to Qatar and Russia only came about thanks to bought votes then the awards could be invalidated,” said Scala told Swiss newspaper SonntagsZeitung. “This evidence has not yet been brought forth.”