Police have appealed for witnesses as they investigate an alleged incident involving Barnsley head coach Daniel Stendel and Fleetwood boss Joey Barton.
Barnsley player Cauley Woodrow wrote on Twitter – in a post that was later delete – that Barton “physically assaulted” Stendel in the tunnel after Saturday’s loss at Oakwell.
South Yorkshire Police confirmed that a man had suffered “facial injuries”.
They are now searching for people “with a view, or in the area of the tunnel”.
In a statement released on Wednesday, South Yorkshire Police said no arrests have been made and that enquiries continue.
“Officers are particularly keen to speak to anyone who may have caught the incident on camera or who may have any mobile phone footage immediately before or after the incident occurred,” the statement continued.
On Tuesday, Barnsley made a formal complaint to both the Football Association and the English Football League.
Fleetwood have said they had “been made aware of an alleged incident” and were “currently establishing the facts”.
Former England midfielder Barton, 36, has a history of controversy, including a 77-day spell in prison for common assault and affray following an incident in Liverpool city centre in December 2007.
He took over at Fleetwood for his first managerial job last summer – one day after an 18-month FA ban for betting ended.