The match will finally begin at 22:05 GMT+1, Arsenal announced. The reasons for the delay are understood to be purely about safety.
The police requested a delayed kick-off after crowd congestion outside the Emirates Stadium. While Cologne fans were allowed into the stadium, the home supporters were kept outside waiting.
Thousands of fans were packed around the outer ring of the Emirates, many of them followers of the Bundesliga outfit. While space for only 3,000 away fans is available, it is understood that up to 20,000 fans were in London today.
The kick-off of #AFCvCOL has been delayed by an hour in the interests of crowd safety
— Arsenal FC (@Arsenal) 14 September 2017
The match between Arsenal and Köln will be delayed for a minimum of one hour in the interests of crowd safety. More details to follow. #UEL
— UEFA Europa League (@EuropaLeague) 14 September 2017