Anti-doping investigator Richard McLaren believes Russian football had a separate cover-up system to conceal positive tests, German broadcasters ARD said on Wednesday.
McLaren told ARD that 155 urine samples could have been part of this cover-up and were yet to be tested. He assumed that the samples were either manipulated or positive, ARD said on their website ahead of the interview to be broadcast later in the day.
The Canadian lawyer and World Anti-Doping Agency (WADA) investigator McLaren had over the past years submitted two reports on wide-ranging and institutionalised doping practices in Russian sport, with only around 30 footballers from 1,000 athletes overall implicated.
The ARD report comes a few days after British paper Mail on Sunday said that all 23 members of the Russian 2014 World Cup squad were being investigated over involvement in a state-sponsored doping programme.
A FIFA spokesman said Wednesday, "in close collaboration with WADA, it is still investigating the allegations involving football players in the so-called McLaren report.
"It is in FIFA's interest that such procedures are finalised as early as possible, since until then FIFA will not be in a position to provide any further details."
McLaren said there was enough evidence for FIFA to appoint a special investigator as he outlined the cover-up suspicion.
"There are ... 155 samples who are waiting analysis and were seized by WADA. We also reported those to FIFA," McLaren told ARD.
"That gives rise to a suspicion: One that there is a bank of clean samples and that it's been used with respect to footballers.
"Either there's been tampering with the caps, so that contents could have been changed or the contents haven't been changed but there may be prohibited substances in there."
ARD said that one of the 155 samples involved a current Russian international player, with emails from 2015 suggesting that the player in question tested positive for a banned stimulant and that the sample was to be swapped.
"We have some information where there is reference to trying to find a sample which would be suitable possibly for swapping," McLaren said.
The latest revelations come during the Confederations Cup in Russia which ends on Sunday, and one year ahead of the World Cup in the country, raising questions whether Russia are the right country to stage the showcase event.
Russia 2018 organizers said only that "Doping controls at the FIFA Confederations Cup and the 2018 FIFA World Cup are entirely in FIFA's competence."
Joachim Loew, the coach of world champions Germany, meanwhile called for proven doping offenders to be banned and FIFA and WADA should make those names public.
"I would like to hear all names in public. I would also like to see FIFA and WADA to name names. No one should be allowed to sweep it under the rug," Loew said.
Russia is aiming to restore its credibility as WADA has allowed the still suspended Russian anti-doping body RUSADA to plan and coordinate testing under international supervision, and some athletes from the banned Russian athletics federation can compete as neutrals.
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