A Leeds United supporter was filmed being struck by a police officer after the Championship side's defeat to Millwall on Saturday.
Footage circulating on social media shows one officer seemingly aiming a violent blow at the fan, after repeatedly asking individuals to 'step back'.
Frustrated supporters had argued with the line of Metropolitan Police officers after safety measures were implemented to keep rivals groups apart around The Den.
The individual on the end of the violent blow was at the front of the group as officers, with some mounted on horseback, attempted to keep order as tensions rose.
Metropolitan Police later released a statement, and confirmed they were aware of the incident and are 'working to establish the full circumstances'.
The statement read: 'Police are aware of a video circulating following the Millwall vs Leeds Utd match at The New Den on Saturday, 5 October showing an altercation between a police officer and a supporter which took place after the match had concluded.
'The footage is a limited capture of an incident in which a large group of people attempted to force their way past officers who were managing crowd control as part of a pre-planned policing operation following the football match.
'We are working to establish the full circumstances of what took place.
'To that end, the matter may be referred to the Met's Directorate of Professional Standards for review if necessary.
'There were no arrests in relation to this specific incident.
'There were three arrests as part of the policing operation: 1 x criminal damage; 1 x coin throwing; 1 x section 4 Public Order.'