Cologne have apologised for the crowd disturbances which overshadowed Thursday night's Europa League match at Arsenal.The Bundesliga club, though, also hit back at their limited ticket allocation and criticised " organisers" for being "not adequately prepared", while insisting the Police presence was "too small". Cologne also claimed some Arsenal tickets had been passed on "for horrendous prices". The Group H opener, which Arsenal won 3-1, was delayed by an hour as many away supporters without tickets looked to gain entry to the Emirates Stadium. It is estimated around 20,000 Cologne fans made the journey to London, despite only 3,000 tickets being on sale. Thousands of away supporters could be seen sat in the home stands. Following the disturbances both inside and outside the ground, governing body UEFA opened disciplinary proceedings on Friday morning against the clubs. Cologne face charges involving crowd disturbances, setting off fireworks, throwing of objects and acts of damage by their fans, while Arsenal are under investigation for having ''stairways blocked'' in the away section. Arsenal insist the safety of supporters was the main concern at the time and promised a ''full review'' would be undertaken to discover how the events were able to occur. Cologne's statement read: "FC Koln is proud that tens of thousands of 'Colognians' wanted to experience the first European match in 25 years and made their way to London. "The overwhelming majority of our fans have represented the club, the city of Cologne, and German football happily and positively. The London locals and the Police shared these feelings on social media leading up to the match. "Due to the enormous demand for tickets, it would have been sensible, not least for security reasons, to allow more than the allocated 5% of stadium capacity to the guest fans. "It was apparent that thousands of people from Cologne would seek to avoid the restrictions and get tickets in every way possible. "Despite the tremendous experience of both the London security forces and Arsenal as a permanent partaker in European football, the organisers were unfortunately not adequately prepared for the task."In our view, the security concept and communication seemed inadequate and the Police force too small."The Bundesliga side said there could be "no excuse or justification" for the actions of "so-called disturbers", with violent scenes of stewards and police being attacked. "We distance ourselves from this explicitly," the Cologne statement continued. "Although FC Koln is not responsible for the acts of these so-called disturbers, we ask our English hosts to accept our apology."