Banks in Switzerland have flagged up 53 possible acts of money-laundering that could be linked to FIFA's 2018 and 2022 World Cup bidding contests, the country's attorney-general said.
Future World Cup hosts Russia and Qatar were not implicated by Swiss federal prosecutor Michael Lauber.
Still, the "huge and complex" case he outlined could potentially force FIFA to re-examine taking the world's most-watched sports event from either country if new evidence proves wrongdoing.
"I don't mind if this has some collateral (damage) somewhere else," Lauber said of his investigation, addressing the media for the first time since the dual Swiss and American criminal probes into FIFA were announced three weeks ago.
In a further sign of legal attacks on FIFA picking up pace, the ethics prosecutor of world soccer's ruling body later confirmed he expected an increased workload linked to the 2018 and 2022 case.
The ethics investigation department "has taken the necessary preparatory measures for this and is prepared to increase its staff numbers at any time if needed," Cornel Borbely said in a rare public statement since succeeding Michael Garcia last December.
There seems little respite for FIFA three weeks after a stunning U.S. Department of Justice indictment alleged a racketeering conspiracy among top soccer officials, and two weeks after FIFA President Sepp Blatter added to the crisis by announcing his plans to resign.
Blatter, who has not appeared in public since, is a target of the U.S. federal agencies who are working with Swiss authorities.
Lauber said Wednesday he "does not exclude" interviewing Blatter and FIFA secretary general Jerome Valcke in the future.
They are not, however, currently under suspicion in a Swiss case prompted by FIFA's own criminal complaint against "persons unknown" last November.
The football body sent Lauber a 430-page investigation report submitted by Garcia, a former U.S. Attorney who resigned from FIFA last December protesting that his work had been misrepresented.
Lauber's office opened a case for suspected "criminal mismanagement and money-laundering" in the bidding contests which involved 11 nations seeking votes from a 24-man FIFA executive committee.
Giving a first detailed account of his ongoing case, Lauber said the 53 "suspicious bank relations" were filed to comply with Switzerland's regulations against money laundering.
Some of the 53 transactions are among 104 incidents previously notified to Swiss and American federal authorities, he said.
The American case alleged that senior FIFA voters received $10 million in bribes to support South Africa's successful bid for the 2010 World Cup. Valcke has acknowledged signing off the transfer from a FIFA account on behalf of South African officials, but said the payment had been approved by Julio Grondona, the former chairman of the finance committee who died last year.
Lauber would not be drawn on whether the South African case was also within the scope of his investigation.
"This is a dynamic process," Lauber said. "It could really go everywhere and that is why I don't want to tell you which direction I put my focus."
Lauber, who led units specializing in organized crime in Switzerland and money laundering in Liechtenstein, said Wednesday that his task force is analyzing nine terabytes of data.
Lauber's team has also picked up one of Garcia's lines of inquiry into payments linked to a friendly match between Argentina and Brazil played in Doha two weeks before the FIFA vote. Both countries had long-serving delegates on FIFA's executive committee.
An executive with Swiss-based marketing agency Kentaro, who worked with the Brazil team in 2010, told The Associated Press he gave evidence to Swiss police on May 27.
Lauber said Kentaro was "a very interesting and very good company" which co-operated with the probe.
The Swiss case could dig deeper into corruption allegations than Garcia, who could not compel some FIFA voters to meet with him and did not have subpoena powers to gather key evidence.
"I have coercive measures and I am independent," Lauber said at a news conference called after his re-election by federal lawmakers for a four-year mandate.
Lauber's team sought to speak in Zurich last month with 10 current and former FIFA executive committee members who took part in the December 2010 hosting votes.
FIFA was thrown into crisis on May 27 with dual raids in Zurich on a luxury downtown hotel and its own headquarters two days before its presidential election. Blatter won despite the crisis.
The Swiss case started much later than the American investigation, which began in 2011. Four men, including former FIFA executive committee member Chuck Blazer of the U.S., entered guilty pleas which were unsealed last month and 14 have been indicted.
Lauber described FIFA as the injured party in his case, which could yet implicate its senior officials.