Borussia Dortmund officials have warned supporters the club will not tolerate any form of discrimination in the stands.
The Bundesliga champions have faced several problems with right-wing fans during the first half of the campaign.
But Dortmund have said these issues are monitored closely and will be addressed appropriately.
"Borussia Dortmund are strictly against any form of discrimination, violence and radical right-wing (tendencies)," a letter to the press, signed by CEO Hans-Joachim Watzke, read.
"Borussia Dortmund explicitly underline that tolerance and diversity are central values in the identity of our club.
"We are proud that we unite and integrate players of different nationalities and religious orientations – from the under-nines to the professional team.
"Responsibility in coherence with extremist remarks from supporters signifies an obligation for Borussia Dortmund to take consequent counter-measures on the foundation of the constitution.
"In order to solve the problem, Borussia Dortmund are highly interested in working constructively with law enforcement, fan organisations and last but not least, the media."