UEFA have appointed an ethics and disciplinary inspector to investigate what happened during Arsenal’s Europa League clash with Cologne on 14 September to cause the heavily-publicised crowd trouble.

Arsenal’s first Europa League clash in 17 years and Cologne’s first in 25 was marred by crowd trouble at the Emirates.

The match was postponed for an hour after an estimated 20,000 Cologne fans descended on the Emirates with thousands dominating the Clock End despite only 3,000 tickets being allocated.

As a result, UEFA appointed an ethics and disciplinary investigator on Friday in hope that they can get to the bottom of how this happened.

“The Control, Ethics and Disciplinary Board has decided to appoint an Ethics and Disciplinary Inspector to initiate the appropriate disciplinary investigations,” European football’s governing body confirmed, reports the Evening Standard.

“The Ethics and Disciplinary Inspector will contact both clubs in order to evaluate the scope of their respective responsibility as regards the incidents connected to this match.”

Cologne currently face four charges: crowd disturbances, setting off fireworks, throwing of objects and acts of damage.

Arsenal have been charged due to stairways in the away supporters’ section being blocked.

Four fans were arrested.

Although Cologne did apologise after the match and have condemned the actions of their fans, they also criticised the lack of policing and what they view as a lack of preparation from the Gunners.

Arsene Wenger said that it would be ‘completely unfair’ for Arsenal to be blamed and insisted that the club were ‘in full consultation with police and UEFA officials on the night and in advance of the game’.

The Gunners won 3-1 after going 1-0 down in the first half through Cologne’s Jhon Córdoba. Sead Kolasinac, Alexis Sanchez and Hector Bellerin all scored to come back and earn three points.