Borussia Dortmund went to the top of the Bundesliga table as they beat Cologne 5-0 at Signal Iduna Park.
Cologne have criticised "inadequate" security measures at the Emirates after crowd issues in their Europa League tie with Arsenal.
UEFA has opened disciplinary proceedings against Arsenal and Cologne following incidents at the Europa League match on Thursday.
Arsenal will hold their own investigation into disturbances after five arrests were made following crowd trouble against Cologne.
Alexis Sanchez's fine strike helped Arsenal to a 3-1 win over Cologne in the Europa League, after the match was delayed by an hour.
Arsene Wenger praised the "exceptional" Alexis Sanchez after his fine goal helped Arsenal to a 3-1 Europa League win over Cologne.
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