The FAI says it's working with Derry City and Bohemians FC in Dublin, following violent scenes before and after a football match in Derry on Friday.
Two people were injured in what the PSNI believes was a coordinated attack.
Detectives in the North are asking people to contact them with any video footage from the clashes.
Tensions flared near Derry’s Lecky Road on Friday night, as two rival groups armed with sticks, bats, and iron bars clashed in a violent confrontation that left property damaged and residents shaken.
The disturbance spread to the Brandywell Stadium area following the Derry City versus Bohemians match, where fireworks and other projectiles were launched into a crowd of away supporters - many of them families with young children.
A teenage boy and a man in his twenties required medical treatment for their injuries.
Police say the earlier violence appears to have been pre-arranged, and officers are now reviewing CCTV and other footage to identify those involved.
The Football Association of Ireland has condemned the scenes and confirmed a full investigation is underway in cooperation with both clubs.
