Arsenal condemned the alleged racial abuse of Kalidou Koulibaly during Thursday's Europa League encounter and have opened an investigation into a video showing a fan shouting slurs at the Napoli defender.
"We utterly condemn use of this type of racist language," the Premier League club said in a statement Friday, according to BBC Sport.
The statement added, "We have launched an investigation to identify the culprit. We operate a zero-tolerance approach and anyone behaving like this is not welcome at Arsenal and will be banned from matches.
"We have an extremely diverse community of fans who are all part of the Arsenal family and such incidents are rare at the Emirates Stadium. We encourage supporters to report any incidents as they happen to stewards or via our matchday alert service."
In a video that emerged on Snapchat during Arsenal's 2-0 victory in north London, a man can be heard calling Koulibaly the N-word, which was also written across the screen.
Koulibaly was the target of racial abuse earlier this season when Inter Milan supporters subjected him to monkey chants.
Arsenal face Napoli in the second leg of their quarterfinal matchup next week in Italy.
The incident comes on the heels of a similar episode involving another English club, as Chelsea banned three supporters who recorded themselves making derogatory remarks aimed at Liverpool star Mohamed Salah.