Her Majesty's Revenue & Customs have released a statement confirming arrests were made as part of an investigation apparently involving both West Ham and Newcastle United.
The London Stadium and Rush Green, plus Newcastle's training ground were raided by police on Wednesday morning and "several" men were arrested, including Newcastle chief Lee Charnley but as yet, no West Ham names have been revealed or linked to suspicious activity.
The HMRC has been working with French authorities as well with arrests being made across the channel, with business records, financial records, laptops and mobile phones seized.
In a statement, HMRC said: "HMRC has arrested several men working within the professional football industry for a suspected Income Tax and National Insurance fraud.
"180 HMRC officers have been deployed across the UK and France today. Investigators have searched a number of premises in the North East and South East of England and arrested the men and also seized business records, financial records, computers and mobile phones.
"The French authorities are assisting the UK investigation, have made arrests and several locations have been searched in France.
"This criminal investigation sends a clear message that, whoever you are, if you commit tax fraud you can expect to face the consequences."
Sky News understands that Newcastle managing director Lee Charnley is among those arrested."