Jose Mourinho insists Paul Pogba fully focused on Europa League semi-final

A FIFA spokesperson told Press Association Sport that the world governing body was looking at the deal through its Transfer Matching System (TMS), the online platform that monitors cross-border transfers.

"We can confirm that FIFA TMS has been requesting information on this matter," said the FIFA spokesperson. "We have no further comment at this stage."

This is understood to be linked to claims that agent Mino Raiola will earn £41million from the world-record deal that last summer saw the French player return to Old Trafford.

Those claims will be explained in greater detail in a forthcoming book called 'Football Leaks: The Dirty Business of Football', written by two journalists from German newspaper Der Spiegel.

The news emerged in the build-up to United's Europa League semi-final second leg against Celta Vigo - a match Mourinho says has not been impacted whatsoever.

Asked if the stories had affected him or Pogba, the United manager said: "No. The question is simple. He asks the facts and, no, he isn't affected."

The book will allege that the Italian-born, Dutch-based agent Raiola will receive payments for acting for the buying and selling club, as well as the player.

Acting for all three parties in a transfer is unusual but allowed under certain circumstances, and all details must be logged with FIFA TMS.

Neither Pogba nor Raiola has commented on the latest developments.

A spokesman for Manchester United said on Tuesday: "We don't comment on contracts.

"FIFA have had the documents since the transfer was completed last August."

The 24-year-old Pogba, who left United to join Juventus in 2012, has been a regular in the Red Devils' midfield this season, scoring seven goals in all competitions.

FIFA's interest in the transfer emerged on Tuesday night, shortly after sweeping changes were announced to its audit, ethics and governance committees.

The replacement of its chief ethics investigator and ethics judge was always likely to be a controversial move and so it has proved, with the ousted pair claiming their exit is "politically motivated" and "the end of the reform process" at FIFA.