UEFA has opened disciplinary proceedings against Galatasaray, Basel and Borussia Dortmund following crowd disturbances during Wednesday night's Champions League ties.
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 at the Emirates Stadium, causing the Group D match against Arsenal to be briefly halted.
At St Jakob Park, a battery appeared to be thrown in the direction of the assistant referee near to the Basel 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, the clubs could be hit by a fine from the European governing body, or be ordered to play matches behind close doors.
A statement on UEFA's website read: "Disciplinary proceedings have been opened following incidents at last night's UEFA Champions League matches."
Arsenal expressed disappointment over the events on Wednesday evening.
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 the ground, 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.
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 last night, which occurred despite extensive searches of away supporters as they entered the stadium and close liaison with police, UEFA and visiting club officials."
