Germany's winning bid for the 2006 World Cup was aided by bribes paid to FIFA executive committee members, the German newsweekly Der Spiegel reported.
Spiegel said on Friday that the German bidding committee set up a slush fund of 10.3m Swiss francs (about $6m at that time) that was contributed in a private capacity by former Adidas chief Robert Louis-Dreyfus.
In response, FIFA, the world football ruling body, said it will investigate the "very serious allegations" as part of an investigation its legal director is conducting with outside counsel.
The bribe money was reportedly used to secure the votes of four Asian representatives on FIFA's 24-member executive committee before the tournament was awarded to Germany on July 6, 2000.
"In what could turn out to be the greatest crisis in German football since the Bundesliga bribery scandal of the 1970s, SPIEGEL has learned that the decision to award the 2006 World Cup to Germany was likely bought in the form of bribes," said the magazine's piece.
The Asian members joined European representatives in voting for Germany, which won 12-11 after Charles Dempsey of New Zealand abstained from the vote.
Of the three Asian representatives still living, Spiegel only identified Chung Moon-joon of South Korea, who was quoted as telling the magazine that "the questions were unworthy of a response."
Spiegel said that both Franz Beckenbauer, the former Germany great who headed the bidding committee, and Wolfgang Niersbach, the current president of the German football federation (DFB), as well as other high-ranking football officials were aware of the slush fund by 2005 at the latest.
Louis-Dreyfus' loan payment was reportedly kept secret - it did not appear in the bidding committee's budget, nor later in the budget of the World Cup organising committee.
Spiegel said Louis-Dreyfus asked for the money back a year-and-a-half before the tournament began. By then it was worth 6.7m euros. Beckenbauer, by then the president of the organising committee, and Niersbach, the vice president, "began looking for a way in 2005 to pay back the illicit funds in an inconspicuous manner," the magazine said.
Spiegel reported that a cover was created with the help of FIFA and that 6.7m euros was transferred to world soccer's governing body as a contribution to an opening ceremony gala that was later cancelled.
"The money had been paid into a FIFA bank account in Geneva. From there, FIFA allegedly promptly transferred the money to a Zurich account belonging to Louis-Dreyfus," Spiegel reported.
Louis-Dreyfus died in 2009.
Earlier Friday, the DFB said it was investigating whether a 6.7m euro payment made by its World Cup organising committee to FIFA in April 2005 for a "cultural program" had been misused.
"As part of its audits the DFB found no evidence of irregularities. Nor was there any evidence delegates' votes were purchased as part of the application process," the DFB said in a statement.
Spokeswoman Pamela Mueller-Niese told The Associated Press that the German Interior Ministry had "no knowledge" of the matter.