LONDON: Arsenal's Europa League group stage match at home to FC Cologne was delayed by an hour on Thursday, with four arrests made for public order offences after extra police had to be deployed at The Emirates Stadium in north London. British media said 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 were playing in European competition for the first time in 25 years. The reports added that the number of away fans around the stadium was preventing home supporters getting in, although the Arsenal fans were eventually able to enter the stadium. The Metropolitan Police said extra officers had been sent to the stadium after scuffles broke out before kick-off. A police statement said: 'Officers are dealing with disorder at the Emirates Stadium where fans have gathered for the Arsenal vs FC Koln match. A policing plan is in place for the game. Additional officers have been deployed.' The police later said four people had been arrested 'on suspicion of public order offences'. 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 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'. Asked if UEFA should take action in the wake of the disturbances, the French coach added: 'They are the only master to analyse the facts, what happened. They will certainly make an inquiry to see what happened, for sure.' 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.