Suspended Fifa president Sepp Blatter suffered a "medical incident" at the weekend, Swiss radio has reported.
According to sources speaking to the station, Blatter - who was provisionally banned from football for 90 days last month amid allegations of corruption - will have to undergo medical checks over the next 10 days.
Reuters news agency reported a spokesman that Blatter was under evaluation for stress, and that he was not in hospital.
And a spokesman told ITV News his condition is "nothing too serious", adding: "He has just been under a great deal of pressure recently."
He said he was "optimistic" Blatter's condition would improve, and he is expected to be back at work at the start of next week after a few days off.
Fifa has confirmed German World Cup winner Franz Beckenbauer and vice president Angel Maria Villar Llona are both subject to investigations by the organisation's ethics committee.
Beckenbauer was a Fifa voter when Russia and Qatar were chosen to host the 2018 and 2022 World Cups respectively, while Villar Llona has sat as vice president on Fifa's executive committee since 1998.
The investigations into both men have been completed and are now awaiting verdict.
A Fifa statement read: "Proceedings relating to the two officials Angel Maria Villar Llona and Franz Beckenbauer have already been passed on to the adjudicatory chamber."
FIFA confirmed it will not allow Michel Platini to stand in the presidential election while his ban from football-related activity remainsRead the full story ›
Michel Platini will step aside from his official duties after he was suspended for 90 days by FIFA's ethics committee on Thursday, UEFA confirmed.
In a statement, European football's governing body said: "Michel Platini is currently suspended and will therefore not perform his officials duties for the time being. As such he did not attend the meeting of the UEFA executive committee today and has cancelled several official trips.
"UEFA is fully aware of its responsibilities under the relevant provisions of the statutes."
Michel Platini has promised to "staunchly" defend himself against claims of wrongdoing after he was suspended by Fifa for 90 days.
The 60-year-old president of Uefa branded the allegations "farcical" and "astonishingly vague", vowing to ensure that his "good faith prevails".
However, in his statement Platini conceded he did not believe the actions by Fifa's ethics committee to be politically motivated because of his candidature for the Fifa presidency.
Despite the farcical nature of these events, I refuse to believe that this is a political decision taken in haste in order to taint a lifelong devotee of the game or crush my candidacy for the FIFA presidency.
I want everyone to know my state of mind: more than a sense of injustice or a desire for revenge, I am driven by a profound feeling of staunch defiance. I am more determined than ever to defend myself before the relevant judicial bodies.
I want to reiterate in the strongest possible terms that I will devote myself to ensuring that my good faith prevails.
Greg Dyke has expressed sadness that corruption has dominated football in the wake of Sepp Blatter's suspension from Fifa.
"I think it was inevitable that Sepp Blatter would be suspended for something but It's a sad day for football that corruption dominates the headlines yet again," Greg Dyke told ITV News.
Dyke added he thought there would be many people pleased at the "final demise" of Blatter and thought it was "pretty obvious" that he would not survive the scandal.
"From the moment when the FBI got involved and knocked on all those doors, I think it was the beginning of the end for Sepp Blatter."
Regarding Michel Platini, Dyke said that if there was any evidence that showed Uefa's boss had committed wrongdoing, then the FA would not support his candidature for Fifa president.
European football's governing body UEFA has expressed its "full confidence" in Michael Platini.
UEFA's president has been suspended from all footballing activities for 90 days by Fifa as investigations into financial wrongdoings continue.
However, in a statement UEFA said it "saw no reason" for Platini to be replaced at the top of the Association and would "stand fully" beghind him.
In light of the events occurring today regarding UEFA President Michel Platini, the UEFA Executive Committee has taken the following decisions on 8 October.
An Emergency meeting of the UEFA Executive Committee will be convened in Nyon on Thursday, 15 October; in addition, all 54 member associations of UEFA will meet at UEFA Headquarters on the same day.
The UEFA Executive Committee saw no need, at this moment in time, to invoke Article 29(5) of the UEFA Statutes, pursuant to which the highest-ranking Vice-President of UEFA may step in to assume the powers and duties of the President in his absence.
This is because the UEFA Executive Committee is aware that the UEFA President will immediately take all necessary steps to appeal the decision of the FIFA Ethics Committee to clear his name. Furthermore, the UEFA Executive Committee stated that there must be a very rapid final decision on this matter before the relevant bodies, in the interests of both justice and football.
Finally, the UEFA Executive Committee expressed its full confidence in UEFA President, Michel Platini, and stands fully behind him.
The scandal enveloping world football's governing body dates back nearly five years.Read the full story ›
The International Olympic Committee has forcefully told Fifa to get its house in order in the wake of the latest suspensions.
The IOC said in a statement that football's governing body had to act urgently to address the "structural problem" in Fifa in order to restore stability and credibility".
Enough is enough. We hope that now, finally, everyone at FIFA has at last understood that they cannot continue to remain passive. They must act swiftly to regain credibility because you cannot forever dissociate the credibility of FIFA from the credibility of football.
FIFA must realise that this is now about more than just a list of candidates. This is also a structural problem and will not be solved simply by the election of a new President.
They must do two things immediately: they must accelerate and deepen the reform process in order to comply with accountability, transparency and all the principles of good governance, as expressed in our reform programme, Olympic Agenda 2020.
They should also be open for a credible external presidential candidate of high integrity, to accomplish the necessary reforms and bring back stability and credibility to FIFA'.
Fifa secretary-general Jerome Valcke has released a statement refuting all allegations against him in the wake of his 90-day suspension.
Jerome Valcke said he is "confident that when all the facts come out, it will be clear that he did absolutely nothing wrong".
Jerome Valcke has unequivocally denied the false allegation made against him. He is confident that when all the facts come out, it will be clear that he did absolutely nothing wrong or improper in carrying out his duties for the good of FIFA and the sport.