UEFA has opened disciplinary proceedings against both Arsenal and FC Koln following their Europa League clash on Thursday night.
The European match was due to kick off at 8.05pm, but was delayed for an hour after thousands of ticketless German supporters attempted to gain access to the Emirates Stadium.
It is thought that as many as 20,000 Koln supporters travelled to London, despite the Bundesliga outfit receiving just shy of 3,000 official tickets for the Europa League contest, which ended in a 3-1 home win.
Arsenal have since announced that they have launched a "full review" following last night's unsavoury scenes, and UEFA has now opened disciplinary proceedings against both clubs involved in the match.
Five charges have been issued to the two clubs, with Arsenal having to answer a charge of having stairways blocked in the away section, which broke safety and security regulations.
Koln, meanwhile, have been hit with four charges relating to crowd disturbances, acts of damage, throwing of objects and the setting off of fireworks during scenes of chaos at the Emirates on Thursday night.
All five cases will be heard by UEFA on September 21.