ZURICH—FIFA President Sepp Blatter was placed under criminal investigation by Swiss authorities Friday as a probe into soccer corruption reached the highest levels and left his grip on the top job in peril.

The Swiss attorney general’s office opened proceedings against Blatter for possible criminal mismanagement and misappropriation of FIFA money. Authorities also searched Blatter’s office and seized data.

The announcements came as FIFA wrapped up a two-day executive committee meeting and marked another stunning day of turmoil for the governing body and Blatter, who have been targeted by American and Swiss investigations into corruption.

The 79-year-old Blatter is set to step down in February as a result of those probes, but Friday’s events made an early exit seem inevitable.

The opening of formal criminal proceedings against Blatter could lead the FIFAinstigated last November when it complained about possible money laundering in the 2018-2022 World Cup bidding contests won by Russia and Qatar.

His right-hand man, FIFA Secretary General Jerome Valcke, was suspended last week after being implicated in a scheme to sell tickets for the 2014 World Cup on the black market.

Friday’s allegations also relate to undervalued World Cup broadcasting contracts for the Caribbean that Blatter agreed to with disgraced former FIFA vice-president Jack Warner in 2005.

“There is as 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.

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Warner, who was a longtime FIFA power broker supporting Blatter at elections, was indicted in the wide-ranging U.S. case