Ryan Harrison has protested his innocence after being accused of racism by fellow American tennis player Donald Young.
The pair met in a heated encounter in the first round of the New York Open on Monday night, with the umpire getting down off his chair at one point during the opening set to keep the two men apart.
Harrison eventually won the match 6-3 7-6 (7/4), after which world number 65 Young tweeted: "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. I thought this was supposed to be an inclusive gentleman's sport."
Harrison, ranked 44, quickly responded with a vehement denial of Young's claims.
He wrote 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% clear me and I encourage anyone with the available resources to find it."
The ATP said in a statement: "The ATP takes any allegations of racial prejudice extremely seriously.
"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."
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