Newcastle managing director Lee Charnley has been released without charge after being arrested on Wednesday morning.
Newcastle and West Ham’s headquarters were raided by authorities investigating a tax fraud probe.
Charnley was taken into custody by the HM Revenue and Customs but is said to have not been formally questioned by authorities.
He was pictured this afternoon returning home.
A statement from Newcastle said: “Newcastle United can confirm that a member of its staff has this morning been assisting HMRC with their inquiries.”
Charnley has overseen promotion at St James’s Park this season and worked with boss Rafa Benitez to rebuild the club.
He expected to return to work tomorrow as Toon begin their preparations for a return to the Premier League, confirmed with their victory on Monday night.
Newcastle and West Ham’s bases were raided on Wednesday morning as part of a joint operation with authorities in France in which they are investigating cases of alleged income tax and National Insurance fraud.
It also believed there were no arrests made at West Ham.
Officers from HMRC also visited Premier League leaders Chelsea on Wednesday morning but no items were seized or arrests made.
French officials, according to local reports, have arrested four football agents, with Marseille’s transfer dealings understood to be under investigation.
The dramatic series of events started with reports of police raids at Newcastle’s St James’ Park and training ground and West Ham’s London Stadium.
Soon after, a spokesperson for HMRC confirmed that its officers, not police, had “arrested several men working within the professional football industry for a suspected £5million income tax and National Insurance fraud”.
The co-ordinated raids, across the UK and France, involved 180 officers, with investigators searching premises in the north east and south east of England and seizing computers, mobile phones and paperwork.
The spokesperson continued: “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.”
A short statement from West Ham later confirmed their offices at the former Olympic stadium were raided but said the Premier League side was “cooperating fully” with the investigation.