The Association of Tennis Professionals on Tuesday said it has launched an internal investigation after a first-round match between two American players at the New York Open boiled over on the court.
The ATP Tour officials say they are reviewing "allegations of racial prejudice" after Ryan Harrison and Donald Young exchanged words in the first set and had to be separated by the chair umpire during a changeover in play on Monday.
"The ATP takes any allegations of racial prejudice extremely seriously," the organisation said in a statement. "A further review of all video and audio recording from the match will take place as this matter is investigated further.
"No further comment will be made until the completion of the investigation."
The two continued their exchange later on their social media profiles.
African-American Young, 28, posted on Twitter after the match: "I'm shocked and disappointed, Ryan Harrison, to hear you tell me how you really feel about me as a black tennis player in the middle of our NY match."
Harrison, 25, who won the match 6-3, 7-6 shot back on Twitter, "The accusations made by Donald Young tonight following our match are absolutely untrue. I'm extremely disappointed that someone would say this in reaction to a lost tennis match. Any video/audio will 100 per cent clear me."
Harrison and Young have met eight times since their first match in 2010, with Harrison holding an 6-2 lead.