Sepp Blatter, the head of football's world governing body FIFA, is being investigated on suspicion of criminal mismanagement, Swiss prosecutors say.
Fifa President Sepp Blatter
The 79-year-old was interviewed by Swiss police, and his office was searched and data seized on Friday.
FIFA was plunged into crisis in May, when seven senior officials were arrested in Zurich at the request of the US. The Swiss launched their own investigation just hours after, amid complaints of possible money laundering in the 2018-2022 World Cup bidding contests won by Russia and Qatar.
Mr Blatter, who has run FIFA since 1998, announced in June his decision to step down as president of the organisation, following claims of corruption.
The Swiss Attorney General revealed that Mr Blatter is suspected of "criminal mismanagement and misappropriation", reportedly linked to deals between Blatter and Jack Warner over broadcasting contracts.
"There is a suspicion that, in the implementation of this agreement, Joseph Blatter also violated his fiduciary duties and acted against the interest of FIFA," the Swiss federal office said.
Mr Blatter is also suspected of making a "disloyal payment" - a payment against the best interests of FIFA - of two million Swiss francs (£1.3m) to UEFA president Michel Platini in 2011.
Mr Platini, who is widely expected to succeed the Mr Blatter as FIFA president next February, has denied any wrongdoing, stating that the payment relates to work that he carried out under a contract with FIFA.
Mr Blatter has maintained his innocence since the scandal began, and his lawyer, Richard Cullen, said he was confident Mr Blatter would be cleared in the inquiry.