UEFA said in a statement that disciplinary proceedings had been opened against Arsenal for "insufficient organisation" and against their visitors for "crowd disturbances, setting-off and throwing of fireworks" during the Premier League side's 4-1 win.
FC Basel will also be probed by UEFA's disciplinary committee after fans threw "missiles" onto the pitch during their 1-0 home win over Liverpool.
The Swiss champions were ordered to play their Europa League quarter-final at home to Valencia behind closed doors last season after their fans caused trouble in a match at Salzburg.
Borussia Dortmund were also charged due to crowd disturbances, including the setting-off and throwing of fireworks, during their 3-0 win at Anderlecht on Wednesday.

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