WADA seized approximately 3,000 samples from the Moscow anti-doping laboratory in December 2014, with 154 of them provided by footballers, and they are currently stored in a lab in Lausanne.

The football samples have been retested but there have been no positives, which is not surprising considering the state-sponsored conspiracy to open sample bottles that were likely to fail tests and refill them with ’clean’ urine.

This was once thought impossible, as the bottles were meant to be tamper-proof, but has now been established as possible by two WADA-funded investigations, two International Olympic Committee (IOC) commissions and two different teams of forensic specialists.

In a statement released to Press Association Sport, a FIFA spokesperson said all sports federations had been waiting for a "standard methodology" to be developed that could prove there had been "surreptitious opening" of the bottles.

That methodology now exists and the IOC has been using it to prosecute cases against Russian athletes who cheated at the 2014 Winter Olympics and Russians who may have wanted to compete at the 2018 Winter Games in February.

Such is the intricate nature of the work, however, only three samples can be analysed and photographed per day, with the Sochi samples taking priority. WADA has told the other federations that non-IOC work will not start until mid-January.

In the meantime, WADA has given them the Moscow lab’s testing data between January 2012 and August 2015 - this new information has been described by experts as a "game-changer" because it provides proof that the Russians were not reporting all of their positive tests to the authorities, as whistle-blowers have already claimed.

FIFA said it has started to analyse this information but claims it is not complete.

"FIFA has asked WADA to provide this missing information and data as soon as possible and has also requested to be given priority for the forensic analysis of stored samples," the spokesperson said.

FIFA also rejected a report in Thursday’s Guardian which suggested its former chief medical officer, Dr Jiri Dvorak, had been sacked because he had started to correspond with the author of one of the WADA-funded investigations, Canadian law professor Richard McLaren.

The spokesperson said FIFA’s Russian investigation has been led by its anti-doping unit ever since McLaren published his preliminary report in July 2016 and "the very same people who initiated the investigations are still in charge today".

Describing the newspaper report as "completely baseless", the spokesperson detailed FIFA’s investigation up to this point and claimed it had been hampered by an inability to question the chief whistle-blower, ex-Moscow lab director Dr Grigory Rodchenkov.

Earlier this month, Dr Rodchenkov’s lawyer told Press Association Sport he had heard nothing from FIFA and said he did not believe it was interested in pursuing cases against Russian officials and players.

The FIFA spokesperson, however, said it had asked WADA for access to Rodchenkov, who fled Russia in November 2015 and is now in witness protection in the United States, and until November 22 was told this was not possible.

On that date, however, a letter was sent to all relevant international federations telling them about the new forensic test, lab data and Rodchenkov’s "availability to testify in individual cases".

As a result, the FIFA spokesperson said it was continuing its investigations, "in close collaboration with WADA", and would impose the "appropriate sanction" when there is evidence to do so.