Arsenal and Koln charged by Uefa following Emirates disturbances

Thousands of German fans made it into the Emirates on Thursday night for Arsenal's Europa League opener

Police dogs guard fans at the away end at Emirates Stadium

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Uefa have opened proceedings against Arsenal and Koln following Thursday night's disturbances which saw thousands of German fans flood the Emirates Stadium for the Europa League clash.

Arsenal face a probe for "stairways blocked in away supporter sector" while Koln have been handed four charges of crowd disturbances, setting off fireworks, throwing objects and acts of damage.

Uefa will now deal with the case on September 21, the governing body confirmed in a statement on Friday.

The Group H tie, in which Arsenal eventually ran out as 3-1 winners, was delayed by an hour after an estimated 20,000 Koln fans descended upon the Emirates, causing severe congestion around the stadium ahead of the initial 8.05pm kick-off.

The visitors were issued with 3,000 tickets but it's believed thousands of German supporters brought tickets among the home sections and despite the best efforts of the ground officials to identify such fans, many of whom wore Arsenal paraphernalia as disguises, there was a strong visible Koln presence within the stadium once the game kicked off at 9.05pm.

Five arrests were made over the course of the evening and Arsenal issued a statement on Friday insisting the safety of supporters was the main concern at the time as the Premier League club "launched a full review" of the events.

Arsenal added that the club will take measures to avoid any repeat of the issues faced on Thursday night.

"Following last night's Uefa Europa League match with Koln we would like to stress that fan safety was always our paramount concern and informed all decisions made," a statement from Arsenal read.

Riot police were brought in to restore order to the situation

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"We have launched a full review into the circumstances surrounding the game and will ensure any lessons that can be learned are used in the future."

After the game, Koln coach Peter Stoger refused to take questions on the crowd disturbances - but Arsenal boss Arsene Wenger admitted he thought the contest would be postponed and said the visiting fans "were very clever" in infiltrating the home sections of the Emirates.

"They (Koln fans) were very clever," he said after the game.

"I don't know how they managed to infiltrate our fans and get everywhere but they did that very well. I don't know if they went through Arsenal membership, on the internet... they did very well.

"I thought they would not play the game, because I can't see the police taking any risk."

Arsenal also said it was "very disappointing" that so many home tickets appeared to have been purchased by Koln supporters via ticket touts after working closely with the Metropolitan Police, who deployed extra numbers once trouble began, and Uefa.

The game was delayed due to severe congestion

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"We worked in full consultation with police and Uefa officials on the night and in advance of the game and had taken extensive steps in advance to prevent tickets being sold to visiting supporters," the club added.

"This included a number of measures including ensuring no tickets were sold via general sale and that no red memberships purchased after the draw were able to be used to get tickets in the home end for this match.

"We also worked with our colleagues at Koln to stop supporters travelling without match tickets.

"The 3,000 tickets issued to Koln fans was in line with competition rules but it is clear many more visiting fans arrived, causing significant congestion and disturbance outside the stadium before kick-off.

"Many tickets were sold through touts and this is very disappointing and something we continue to work hard to address."