It is reported that a teenager suffered head injuries during trouble that followed Derry City's 2-1 defeat to Dundalk in an FAI Cup semi-final replay at Brandywell Stadium.
Police have confirmed they have received a formal complaint following the violence that flared after the match last night.
A teenager suffered a head injury, which is not thought to be serious, while a Dundalk supporters' bus was vandalised during the trouble.
Chief Inspector Gordon McCalmont said police had built a close working relationship with Derry City football club and the local community over the years are also disappointed over what transpired last night following the match.
Anyone who witnessed the disorder or who could assist police in their inquiries is asked to come forward.
Chief Inspector McCalmont said police will meet with the community and the club in the coming days and review this incident and reaffirm their commitment to safe events at Derry city football club.