The Gunners enjoyed a brilliant evening on the pitch, with Gabriel Martinelli starring in the victory at Elland Road.
Manager Mikel Arteta's side cashed in against a depleted Leeds side, who were without 10 first team players through injury and suspension, but the Londoners' classy display was marred by football's latest racist incident.
Arteta said: "Yes, unfortunately I can confirm that. It was reported to the stadium manager. The authorities will deal with that.
"The players that were sitting on the bench. One of those heard those comments.
"I don't know exactly [who was targeted], that's why they will have to be interviewed by the authorities."
Referee Andre Marriner briefly halted play in the 34th minute to consult with match officials after the abuse had been reported where Rob Holding was seen alerting the fourth official.
Arteta added on Sky Sports: "But it was a single person and I don't think that merits a full stadium to pay the price.
"It was a single incident, it has to be reported. It was reported and now the authorities will have to work with the clubs to try to understand what happened."
In a statement Leeds said: "Racism will not be tolerated at Leeds United and any supporter found to be using racist language will be subject to a life time ban for all Leeds United games.
"We can confirm that an investigation into claims of racism during the first half of our game with Arsenal today are underway and that one arrest has been made in connection to the allegation."
Leeds manager Marcelo Bielsa was also asked about the incident in his interview with Sky Sports. He said: "Of course I am against all acts of discrimination."