Arsenal could be fined by Uefa following crowd disturbances during Wednesday night's Champions League tie against Galatasaray, with the Turkish club likely to face much more severe sanctions after their supporters threw flares onto the pitch at the Emirates Stadium.
The governing body on Thursday confirmed disciplinary proceedings had been opened against four teams - Arsenal, Galatasaray, Basle and Borussia Dortmund - in the wake of incidents during Wednesday night's European ties.
At the Emirates Stadium, several flares were thrown onto the pitch from the section where the 3,000-strong travelling Galatasaray supporters were located towards the end of the first half, causing the Group D match to be briefly halted.
Metropolitan Police confirmed there had been six arrests as part of their operation for the European tie in north London, two of which were for entering the ground with flares.
Arsenal 4 Galatasaray 1 - player ratings
Arsenal 4 Galatasaray 1 - player ratings
1/11 Wojciech Szczesny
Rush of blood to the head got himself needlessly sent off, and put his team under pressure for the final half-hour. 4
2/11 Calum Chambers
Joined up with the Arsenal attacks well, and had no problems defensively. 6
3/11 Kieran Gibbs
A constant outlet going forward with his pace and direct running – crucial for Arsenal’s threadbare defence that he stays fit. 6
4/11 Per Mertesacker
Composed on the ball, and made a few important interceptions. 6
5/11 Laurent Koscielny
Had very little to do, but denied Burak Yılmaz space in which to operate. 6
6/11 Mathieu Flamini
Got about his work quietly and efficiently, without having to do anything spectacular.
7/11 Alex Oxlade-Chamberlain
Another very impressive display from the winger, full of direct running and incisive passing. Assist for Welbeck’s third goal was the highlight. Rested for the final 20 minutes. 7
8/11 Santi Cazorla
Never stopped running and so unlucky not to score when delicate chip was cleared off the line in the final minute.. 6
9/11 Mesut Ozil
Flitted in and out of the game – showed some nice touches, and lovely through ball for Sanchez’s goal, but hustled out of it too easily on a couple of occasions. 6
10/11 Alexis Sanchez
Provided a perfectly weighted pass for Welbeck’s first and took his goal with aplomb. Sacrificed for Ospina when Szczesny was sent off. 8
11/11 Danny Welbeck
Finished all three of his goals clinically and showed for the ball in tight areas time and again. Superb. 9
Uefa view it as the home side's responsibility to search supporters for any illegal items before they come into the stadium.
There were disturbances before the match, when Galatasaray fans had let off flares in streets around Finsbury Park and thrown some into the Tollington Arms pub.
A strong police presence was on hand, including officers in riot gear and with dogs, while Arsenal stewards conducted searches of bags on the turnstiles, when half-a-dozen flares and fireworks were confiscated, although some were able to be smuggled in by Turkish supporters.
Video: The Independent's look ahead to this weekend's Premier League action
Arsenal reported damage to around 100 seats in the away end and will now co-operate fully with Uefa when asked for their observations.
An Arsenal spokesman said in a statement to Press Association Sport: "Crowd safety is always a top priority for us and we were disappointed with the incidents on Wednesday night, which occurred despite extensive searches of away supporters as they entered the stadium and close liaison with police, Uefa and visiting club officials."
Elsewhere, in Switzerland at St Jakob Park, a battery appeared to be thrown in the direction of the assistant referee near to the Basle goal during the tie with Liverpool, while at Anderlecht's stadium, flares were lit in the area housing travelling Borussia Dortmund fans.
If found guilty, as well as fines, the clubs could be ordered to play matches behind closed doors. That sanction was imposed on Basle, one game suspended for two years, after a similar incident in a Europa League game against Salzburg in March on top of a hefty £100,000 penalty.
A statement on Uefa's website, updated on Thursday evening to add reference to Arsenal's charge for what is understood to be a minor possible redress, read: "Disciplinary proceedings have been opened following incidents at last night's Uefa Champions League matches:
"Match: Uefa Champions League Group B match between Basle and Liverpool (1-0) played on Wednesday 1 October in Switzerland.
"Basle: Throwing of missiles (art. 16 (2) (b) DR)
"Match: Uefa Champions League Group D match between Arsenal and Galatasaray (4-1) played on Wednesday 1 October in England.
"Galatasaray: Crowd disturbances (art. 16 (2) (f) Disciplinary regulation); setting-off and throwing of fireworks (art. 16 (2) (b) & (c) DR)
"Arsenal: Insufficient organisation (art. 16 (1) DR)
"Match: Uefa Champions League Group D match between Anderlecht and Borussia Dortmund (0-3) played on Wednesday 1 October in Belgium.
"Borussia Dortmund: Crowd disturbances (art. 16 (2) (f) Disciplinary regulation); setting-off and throwing of fireworks (art. 16 (2) (b) & (c) DR)
"All three cases will be dealt by the Uefa Control, Ethics and Disciplinary Body on October 16."
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