Police have confirmed that the Wests Tigers star and New Zealand captain is being investigated over the incident with a 24-year-old man, which started with an verbal altercation in the early hours of Saturday in Sydney.
Marshall's manager Martin Tauber told Sunday newspapers that Marshall had been racially abused by a group of eight to 10 people.
"One of them started to shout at him and said: 'Go back to New Zealand you black ****'," Tauber told The Sunday Telegraph.
"He (Marshall) tried to walk away from him - he tried to make light of it and then the guy did it again."
The incident at about 3.20am (AEDT) on Saturday happened after Marshall had hosted Footy Rocks, a fundraiser for the Children's Cancer Institute of Australia.
The 24-year-old reportedly sustained a small facial cut and reported the incident to The Rocks Police Station.
Last week Marshall became the face of the NRL's 2011 season and declared he "wants to be the player that kids want to be when they grow up".
Wests Tigers said in a statement on the club's website that Marshall had briefed it on all the circumstances of the incident and would cooperate with police inquiries.
"It would be inappropriate for the club to make any further comment at this stage."
