Fifa looking into Russia football doping claims from McLaren report
Fifa says "it is still investigating allegations" that footballers were involved in a state-sponsored doping programme in Russia.
At least 30 sports, including football, covered up samples involving more than 1,000 athletes between 2011 and 2015, according to the McLaren report.
The Mail on Sunday has said Fifa was investigating if Russia's 2014 World Cup squad were part of the programme.
However Fifa says no players from the competition returned a positive test.
"Fifa has simply confirmed that, in close collaboration with Wada [World Anti-Doping Agency], it is still investigating the allegations involving football players in the so-called McLaren report," said a spokesman from world football's governing body.
"However, Fifa did not refer to any particular players, since it cannot comment on the status of ongoing investigations."
Wada added that it "eagerly awaits the outcomes" and that it has "the right to appeal against any decision" where a governing body chooses not to raise an anti-doping rules violation.
The second of two McLaren reports, led by Canadian law professor and sports lawyer Dr Richard McLaren, was published in December 2016.
It alleged that Russian authorities assisted athletes taking banned drugs by swapping their positive samples for clean ones.
But Fifa said that samples taken from players at the 2014 World Cup, including the full Russian squad, were sent to a Wada-accredited laboratory in Lausanne, Switzerland.
It added that the same procedure is being applied for this year's Confederations Cup, which is being held in Russia as a dress rehearsal for the 2018 World Cup.
"As far as the Fifa Confederations Cup is concerned, every participating player has been tested through blood and urine in unannounced controls," added Fifa.
"Both the results of the unannounced and the post-match tests have been negative so far."
Russia went out at the group stage of the 2014 World Cup after two draws and a defeat.
Professor McLaren confirmed that 33 football players, including some foreigners, were listed in his report, although no other details were revealed with information passed on to federations and regulatory bodies.
"There have never been and will never be any problems with doping in our football - our team are permanently being tested, they undergo doping tests after every match," Russia's deputy prime minister Vitaly Mutko told TASS news agency.
The McLaren reports looked into allegations made by Dr Grigory Rodchenkov, a director of the anti-doping laboratory at the Sochi Winter Olympics in 2014.
The first McLaren report said positive drug tests were secreted through "mouse holes" and swapped for clean negative ones.
Wada recommended all Russian competitors be banned from Rio 2016, but the International Olympic Committee (IOC) left it up to individual sports' governing bodies to decide.
Only the International Association of Athletics Federations enforced a blanket ban, which is still in force for this summer's World Athletics Championships in London.