It is believed that secret payments made to players and agents are the reasons behind the HM Revenue and Customs (HMRC) raids at football clubs.
West Ham and Newcastle’s grounds were raided on Wednesday, 26 April, as part of a tax fraud investigation.
It is now suspected that serious tax fraud was committed during the transfer of players between French and Premier League clubs, with an estimated amount of £5m being involved.
French authorities say that 10 searches were carried out in France and four people were placed in police custody.