Fifa president Sepp Blatter is being investigated by US officials as part of their inquiry into corruption at the world football body, US media say.
The news came hours after Blatter, 79, announced that he was stepping down from his role.
US prosecutors launched a criminal inquiry last week, with seven Fifa officials arrested in Switzerland, part of a group of 14 people indicted.
Two days after the arrests, Blatter was re-elected president of Fifa.
However, he said on Tuesday that it appeared the mandate he had been given “does not seem to be supported by everybody in the world of football”.
Blatter said Fifa needed profound restructuring, adding that he would remain in post until an extraordinary congress was called to elect a new president.
No dates have been set, but under Fifa rules it is expected to take place between December 2015 and March 2016.
US officials quoted in the New York Times said they hoped to gain the co-operation of some of the Fifa figures now under indictment on charges of racketeering and money laundering to try to build a case against Blatter.
Separately on Wednesday, Interpol issued a wanted persons alert for two former Fifa officials, Jack Warner and Nicolas Leoz, as well as four corporate executives. All six were on the list of 14 people indicted by the US authorities last week.
Meanwhile, South African’s sports minister has again denied that a $10m bribe was paid to secure the 2010 World Cup, which was one of the charges to come out of the US investigation.
Earlier the FBI, Internal Revenue Service and the US Attorney for the Eastern District of New York, who is involved in the US prosecutions, all said they would not comment on the Blatter resignation.
In its prosecution, the US justice department said 14 individuals were under investigation worldwide for allegedly accepting bribes and kickbacks estimated at more than $150m (£97m) over a 24-year period.
Two vice-presidents were among the seven Fifa officials arrested in Zurich. They all await US extradition proceedings.
Uefa chief Michel Platini said an emergency meeting scheduled for Saturday to discuss the Fifa crisis and Blatter’s re-election – a move the European body had opposed – would now be postponed.
Mr Blatter, who is Swiss and has been Fifa president since 1998, said he would urge Fifa’s executive committee to organise an extraordinary congress “for the election of my successor at the earliest opportunity”.
Further allegations of corruption emerged on Tuesday with claims that Fifa general secretary Jerome Valcke was linked to an alleged $10m (£6m) payment of bribes over South Africa’s bid to host the 2010 World Cup. He denies any wrongdoing.
South African Sports Minister Fikile Mbalula told reporters on Wednesday that the payment was above board, aimed at supporting football in the African diaspora in the Caribbean.
“We refuse to be caught up in a battle of the United States authorities and Fifa,” he added.
A separate criminal investigation by Swiss authorities into how the 2018 and 2022 World Cups were allocated is also under way.
Australian football chief Frank Lowy said on Wednesday that the race to win the 2022 bid, which was awarded to Qatar, was “not clean” and that he had shared what he knew with the authorities.
He said in an open letter that former Concacaf president Jack Warner had misappropriated funds worth $500,000 sent by Australia intended to develop the organisation’s Centre of Excellence in Trinidad and Tobago.
Blatter’s departure “should open the door to major reform,” he added. The Australian government spent about $40m on its World Cup bid but received only one vote.