The start was delayed by one hour as away fans, many of them without tickets, were preventing home supporters getting in.
Arsenal's Europa League group stage match at home to FC Cologne was delayed by an hour on Thursday. Extra police had to be deployed at The Emirates Stadium in north London to control the crowd while four people were arrested for public order offences.
According to reports, about 20,000 Cologne fans had made their way through London towards the ground despite only 3,000 tickets being allocated to the German club, who are playing in European competition for the first time in 25 years.
The reports added that the number of away fans around the stadium were preventing home supporters getting in, although the Arsenal fans were eventually able to enter the stadium.
The Metropolitan Police said extra officers were sent to the stadium after scuffles broke out before kick-off.
Asked if the number of Cologne fans at the match was a surprise, Arsenal manager Arsene Wenger told reporters: "They were very clever. I don't know how they managed to infiltrate our fans and get everywhere but they did that very well."
"Were the problems created by people who had no tickets? I don't know. But certainly they (Cologne) had more people here than tickets so that was certainly the cause," he said at the post-match news conference.
"I've followed German football for a long time and I thought Cologne had not played in Europe for 25 years. On the first night they go out (to play), they spoil their night. I couldn't understand that."
The Group H game, which Arsenal won 3-1, was due to kick-off at 1905 GMT (0035 IST on Friday) but European soccer's governing body UEFA, which organises the competition, said 45 minutes before the scheduled start it would be put back "in the interests of crowd safety".
Once the match got underway Arsenal fell behind to a stunning long-range strike by Cologne forward Jhon Cordoba before second-half goals by Sead Kolasinac, Alexis Sanchez and Hector Bellerin secured victory for the Premier League side.
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
 "Arsenal vs Cologne")
)
)
)
)
)
)
)
)
)
)
)
)
)
)
){kind=small}
){kind=small}
){kind=small}
){kind=small}
)
){kind=small}
){kind=small}
)
)
)
)
)
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}