- Video report by ITV News Correspondent Peter Smith
Newcastle United and West Ham United's grounds have been raided in connection with suspected income tax and national insurance fraud in the football industry.
Newcastle's managing director, Lee Charnley, was arrested as part of the investigation, which also saw Chelsea's ground visited by HMRC officials.
ITV News understands Mr Charnley has since been released without charge.
HMRC confirmed "several men" were held after early-morning raids by tax authorities in the UK and France.
No one from West Ham has been arrested and the Premier League club said it is "cooperating fully with HMRC to assist their enquiries".
Chelsea confirmed its premises were visited by the HMRC "in connection with its wider investigation" though the club was not raided.
"HMRC has requested certain information which the club will provide," the Premier League club said in a statement.
ITV News Sports Editor Steve Scott said the HMRC's overall investigation is two-fold - examining the tax paid by footballers and the tax paid on transfer deals - with the club raids believed to be in relation to the latter.
"Transfer deals generate an awful lot of cash for an awful lot of people," he said.
"We've seen a letter today from an agent instructing his solicitor to split his fee six different ways."
At least 180 officers were involved in the operation involving tax authorities in the UK and France.
The raids saw business and financial records, computers and mobile phones seized in the raids.
HM Revenue and Customs refused to confirm the clubs involved but said premises in the north-east and south-east of England had been raided as well as locations in France.
Newcastle managing director Charnley, 39, became boss of the Mike Ashley-owned club three years ago.
His arrest comes two days after the Championship side sealed their promotion back to the Premier League at the first attempt.
A statement from Newcastle confirmed "a member of its staff has this morning been assisting HMRC with their inquiries".
Damian Collins, chair of the Culture Media and Sport Select Committee, told ITV News the raids raised questions over the conduct of both the clubs and the tax investigators.
"This is a big issue for the tax authorities to be involved on raids on these clubs on this scale shows there must be a major problem they're concerned about," he said.
"There are quite strict rules for clubs about paying their taxes on time and football authorities say they enforce those so people will rightly question how it's been possible for this issue to arise in the first place."
An HMRC statement confirming the arrests said: "This criminal investigation sends a clear message that, whoever you are, if you commit tax fraud you can expect to face the consequences.
"As this is an ongoing investigation, HMRC is unable to provide any further detail at this time."