FIFA has opened an investigation into Paul Pogba's world-record transfer from Juventus to Manchester United.

Following multiple reports in France, a FIFA spokesperson confirmed that its Transfer Matching System "has been requesting information on this matter," but would not comment further.

It is not yet clear what aspect of the Frenchman's £89 million move transfer FIFA is investigating. Some news outlets hypothesised that it could surround agent Mino Raiola, who reportedly pocketed £41m from the deal.

The investigation was revealed in the same week the book "Football Leaks: The Dirty Business of Football," which claims to reveal details of the Pogba deal including Raiola's cut, is due to be published in Germany.

A United spokesperson said that the club "do not comment on individual contracts," but added that, "FIFA have had the documents since the transfer was concluded in August." Raiola declined to comment to The Times.

However, sources told ESPN FC that United are confident everything will be found to be in order and, asked if the stories had affected him or Pogba, United manager Jose Mourinho told a news conference ahead of the Europa League semifinal second leg: "No. The question is simple. He asks the facts and, no, he isn't affected.''

Pogba, 24, started his career at Le Havre before joining United in 2009. He left Old Trafford for Juventus in 2012 after making just seven first-team appearances.

He returned as the world's most expensive footballer and has scored seven goals in 48 games this season.

The protracted transfer saga over the summer meant Pogba was not signed in time to play in United's first game of the season -- a victory over Leicester in the Community Shield.

He also missed the first Premier League game of the season after a suspension picked up in Serie A was carried over, before eventually making his second United debut in a 2-0 win over Southampton at Old Trafford on Aug. 19.

After being left on the bench for the defeat at Arsenal on Sunday, Pogba is set to start United's Europa League semifinal second leg against Celta Vigo on Thursday.

Jose Mourinho's side hold a 1-0 lead after the first leg in Spain and are looking to book their place in the final in Stockholm later this month.