A Leeds United fan was struck by a police officer amid unrest after their clash with Millwall on Saturday.
A clip circulated on social media showed a line of Metropolitan Police officers, including three on horseback, holding back a group of Leeds fans.
Previous clashes between Leeds and Millwall have generated violence leading to measures being taken to keep rival fans appart.
As frustrated fans argued with police, one man at the front of the group was filmed being on the receiving end of a violent blow from one of the police officers.
The officer was seen repeatedly asking fans to "step back" as they looked to keep order.
A Leeds fan named Steve Davies replied to the video footage stating: " @metpoliceuk please can you identify this officer who assaulted someone today and also verbally abused me."
The clip was filmed and posted by another Leeds supporter, captioned: "Call this sensible crowd control @LUFC ???"
A statement from the Metropolitan Police 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."
Millwall claimed a 2-1 win at The Den, with Jed Wallace penalty and Tom Bradshaw strike enough to secure three points.
Ezgjan Alioski pulled one back for the visitors, but they were unable to find an equaliser having been reduced to 10 men when Gaetano Berardi was sent off after less than a quarter of an hour.
The result leaves Leeds fifth in the table, losing ground on the leaders, whilst Millwall moved up to 15th after a victory in their first game under caretaker boss Adam Barrett following the resignation of Neil Harris.
"It's been a very eventful 48 hours, an absolute whirlwind," Barrett told BBC London after the game.
"To come through it on the back of that with three points, and the performance against a top, top side I'm absolutely delighted for everyone at the football club.
"I thought the lads played some excellent stuff at times and created chances, so I was delighted."
