Scottish champions Celtic on Thursday announced an investigation into violent clashes between supporters and police ahead of their Champions League defeat by Ajax in Amsterdam.
Dutch police arrested 44 people, including 28 from Scotland, after fans armed with bottles and sticks reportedly attacked plain-clothed officers prior to Wednesday's Group G fixture.
Eight police officers were injured in the disorder.
Celtic pledged to launch a probe, but claimed that their supporters had been "subjected to a high degree of provocation".
"Celtic Football Club is currently investigating events in Amsterdam last night (Wednesday)," read a statement from the club.
"We have been informed that there are five individuals detained in Holland. We are not clear if they have any formal association with the club, however, we will be liaising with the local authorities in Amsterdam, our own police and the British Consulate in order to fully understand events.
"We would stress that there is no excuse for any form of violent conduct. In addition, we have received numerous complaints from Celtic supporters in relation to their treatment in Amsterdam, which we will also investigate fully.
"There is no question that Celtic supporters have been subjected to a high degree of provocation."
Celtic also claimed that a group of their fans was subjected to an "organised attack" the night before the game, two weeks after Ajax fans had allegedly thrown missiles and damaged seats in the reverse fixture at Celtic Park.
European governing body UEFA opened disciplinary proceedings against Ajax over their supporters' conduct in Glasgow last month, with a disciplinary case due to be heard on November 21.