Swiss prosecutors have opened a criminal investigation into Sepp Blatter, the head of football’s world governing body Fifa.
The attorney general’s office said he was being investigated “on suspicion of criminal mismanagement as well as – alternatively – on suspicion of misappropriation”.
Mr Blatter was being questioned, and his office was searched, it added.
Fifa said it was co-operating with the investigation.
Mr Blatter, 79, has run Fifa since 1998 and has always denied any wrongdoing.
The Swiss attorney general’s office said the investigation surrounds a TV rights deal Mr Blatter signed with former Caribbean football chief Jack Warner in 2005.
Mr Blatter is also suspected of making a “disloyal payment” of two million Swiss francs ($2m; £1.3m) in 2011 to Michel Platini, the head of the European football body Uefa, the statement said.
It said the payment was “at the expense of Fifa, which was allegedly made for work performed between January 1999 and June 2002”.
Mr Blatter is due to step down in February. Mr Platini is widely expected to replace him.
Analysis by BBC sports editor Dan Roan
Ever since May, when the arrest of senior Fifa officials in dawn raids in Zurich plunged world football’s governing body into crisis, the sport has wondered whether the scandal would lead directly to President Sepp Blatter.
Today – finally – it did. On the one hand, perhaps it should come as no surprise.
After all, Mr Blatter has been at the helm of Fifa for 17 years. He’s become symbolic of the many corruption allegations that have blighted the body and some thought it a matter of time until investigations by the FBI and Swiss criminal authorities would implicate him.
In fact, such was the perceived threat facing Mr Blatter that his lawyers advised him not to travel abroad.
However, this is still a stunning development, with criminal proceedings opened against the man who still runs world football.
Although Mr Blatter announced he was stepping down back in June, he decided to hang on as president until February in a bid to influence the choice of his successor and reforms. That now seems highly unlikely, with calls for him to resign immediately bound to intensify.
In May, Swiss authorities arrested seven Fifa officials in Zurich at the request of the US. They face extradition.
The US then unveiled indictments against seven other people in their corruption case, nine of whom are high-ranking officials. The Swiss then opened their own investigation into Fifa, hours after the initial arrests.
Mr Blatter won a fifth consecutive Fifa presidential election on 29 May but, following claims of corruption, announced his decision to step down on 2 June. He is due to finish his term at a Fifa extraordinary congress on 26 February.
Fifa cancelled its news conference on Friday only minutes before it was due to start.
Mr Blatter would have been speaking in public for the first time since general secretary Jerome Valcke was suspended last week amid allegations regarding ticket sales at the 2014 World Cup.
Newspaper reports implicated Mr Valcke, 54, in a scheme to sell tickets for above face value.
Mr Valcke, who describes the allegations as “fabricated”, has been released from his duties pending an investigation.
Fifa also announced earlier that it had moved its next executive committee meeting from Tokyo to Zurich.
Correspondents say that, although Mr Blatter has not been indicted, he might be more vulnerable to an extradition request outside of Switzerland.