Supporters of Dortmund allegedly threw pyrotechnics at visiting Copenhagen.
The Danes should then have responded by doing the same thing back, reports the Danish newspaper BT.
The newspaper has spoken to the police, who confirm the course of events but do not want to comment further.
- It is a scandal.
I have commented on many Champions League matches but never seen anything like this, they should be ashamed, says the Danish commentator Niels Christian Frederiksen according to BT.
- Insane scenes, says the newspaper's seconded reporter Lasse Vøge.
The match starts at 18.45 and the Swedish national team midfielder Viktor Claesson can be found from the start.