Millwall have said that they will indefinitely ban fans found guilty of violent behaviour.
The club's CEO Andy Ambler said in a statement: "Our position is clear. Anyone associated with our club found guilty of violent behaviour will be banned indefinitely from Millwall matches in addition to any punishment they receive from the authorities.
"Having worked so hard to show the positive side of our club both on and off the field, we cannot allow the actions of a mindless minority to undermine that.
"At this stage we are still in the process of establishing the full details of what happened in a section of the ground during the second half. When we have those facts at our disposal and the police have completed their investigations, we may be in a position to comment further."
The Metropolitan Police are continuing to investigate.