Fifa did extra doping tests on Russia's World Cup 2014 squad - ex-medical chief
Fifa conducted extra doping tests on Russia's 2014 World Cup squad, the organisation's former chief medical officer Jiri Dvorak says.
President Gianni Infantino says Fifa is still investigating allegations Russian players benefited from a state-sponsored doping programme.
Professor Dvorak told BBC Sport all testing of the Russian squad was done correctly and came back negative.
He said Fifa used an "extra regime" due to rumours around Russian athletes.
Those rumours were regarding the use of xenon, which was added to the World Anti-Doping Agency's (Wada) prohibited list after the World Cup in September 2014.
Professor Dvorak said the gas - which can encourage the growth of red blood cells that boost stamina - was used by some Russian athletes in the 2014 Sochi Winter Olympics by inhalation.
"We heard some rumours about xenon in Russia, so we decided to test that," he told BBC Sport.
"We just tested the Russian team for that because the substance was unknown in the rest of the world. All tests were negative."
How does Fifa test footballers?
Deciding who to test and for what substance is up to the discretion of the chief medical officer of world football's governing body.
Before the 2014 World Cup in Brazil, Fifa confirmed to BBC Sport it tested 800 players through blood and urine in unannounced controls.
This accounted for 91.5% of players included in the final lists for the competition, with the remaining players tested unannounced throughout the tournament.
Fifa was in charge of the tests and sent all samples to be analysed by the Wada-accredited laboratory in Lausanne, Switzerland.
It says the same procedure is currently being applied for the Confederations Cup in Russia, which will host next year's World Cup.
"Both the results of the unannounced and the post-match tests have been negative so far," it added.
Fifa still investigating doping allegations
At least 30 sports, including football, covered up samples involving more than 1,000 athletes between 2011 and 2015, according to the McLaren report.
Fifa refused to say if any of Russia's 2014 World Cup squad are included - though the Mail on Sunday has said they are.
Infantino said he did not know how long the investigation would take.
Speaking publicly on the matter for the first time, he underlined Fifa's position that all Russian players at the last World Cup were tested by world football's governing body and that the results were negative.
He said the same applied to last year's Euro 2016 tournament in France, where European body Uefa conducted the tests, and to international club competitions.
"These tests are not done in Russia," Infantino said. "It's all done outside Russia in Wada-accredited laboratories and they have given negative results.
"These are the facts that need to be remembered. We have all seen the different reports, we are collecting information and if there have been any anti-doping violations, measures will be taken.
"We always have a zero-tolerance policy for doping."