Valencia confirmed on Monday that the club has identified one of the fans that appeared on a video making Nazi salutes and monkey gestures towards Arsenal supporters during Thursday's Europa League semifinal first leg at the Emirates stadium.
A Valencia spokesman told ESPN FC they opened disciplinary proceedings against an unnamed fan with a view to having his club membership taken away.
They are also working to identify the other fans that appeared in the video that circulated on social media after Arsenal's 3-1 win.
The footage showed a small section of Valencia supporters making monkey gestures and fascist salutes.
Both clubs condemned the incident and asked witnesses to come forward so that action could be taken against the individuals.
UEFA's disciplinary body is reviewing the incident.
Six Valencia fans and eight Arsenal supporters were ejected from the Emirates stadium on Thursday for inappropriate behaviour.
Valencia reiterated they have zero tolerance for this type of behaviour and does not anticipate having any similar incidents at the Mestalla stadium in Thursday's return leg "as it has never happened before."