Criminal proceedings have been opened against FIFA president Sepp Blatter by Swiss authorities.
Mr Blatter is suspected of criminal mismanagement or misappropriation, the Swiss Attorney General revealed.
He was interviewed today by Swiss police. Mr Blatter's office was also searched and data was seized.
He is suspected of making a "disloyal payment" of two million Swiss francs to UEFA president Michel Platini.
Under Swiss law, a payment is classified disloyal if it is against the best interest of the employer - in this case FIFA.
Mr Platini, who is the favourite to succeed the outgoing Mr Blatter as FIFA president next February, was a personal adviser to his former mentor when he started out in football politics.
The payment by Mr Blatter from FIFA funds was "allegedly made for work performed between January 1999 and June 2002," the attorney general's office said.
Mr Platini has given evidence as a witness.
The allegations also relate to World Cup broadcasting contracts Mr Blatter agreed to with disgraced former FIFA vice president Jack Warner in 2005.
"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.
Blatter was interrogated after chairing a meeting of FIFA's executive committee on Friday.
The 79-year-old Swiss had been set to hold a news conference for international media after the meeting, but it was first postponed and then suddenly cancelled.
Blatter is the first person to be formally quizzed as a suspect in the Swiss case.
The case was instigated amid complaints about possible money laundering in the 2018-2022 World Cup bidding contests won by Russia and Qatar.
In a statement FIFA said: "Since 27 May 2015, FIFA has been cooperating with the Office of the Swiss Attorney General (OAG) and has complied with all requests for documents, data and other information.
"We will continue this level of cooperation throughout the investigation.
"Today, at the home of FIFA, representatives from the Office of the Swiss Attorney General conducted interviews and gathered documents pursuant to its investigation.
"FIFA facilitated these interviews as part of our ongoing cooperation. We will have no further comment on the matter as it is an active investigation."
