Officials and police are investigating claims by Manchester City's Gael Clichy that a banana was thrown onto the pitch at a friendly between Limerick and City in Ireland on Sunday.
Republic of Ireland Gardai and Limerick officials are studying CCTV footage as they try to identify the spectator responsible for the incident during City's 4-0 win at Thomond Park.
In a statement, Limerick FC said: "The Gardai and stadium officials are reviewing the CCTV recordings to attempt to identify an individual involved in the throwing of an offensive object onto the playing field.
"Any individual identified as being involved in an incident of this nature will be banned from future attendance and the matter will be handed over to the Gardai."
The statement said "all those involved with the friendly game fully condemn all forms of unacceptable behaviour of this nature."
City are not believed to have made a formal complaint about the incident, but Clichy tweeted: "How sad to see bananas thrown on the pitch tonight... Knowing people around the world need food."
News of the investigation came as Newcastle asked Den Haag to investigate reports of racist chanting from sections of home fans during the friendly game between the two clubs on Saturday.
Newcastle striker Demba Ba has criticised spectators who chanted abuse during the match at the Netherlands club's Kyocera Stadium. Reports said not all the Newcastle players heard the abuse, but that midfielder Cheick Tiote had voiced his anger after the 0-0 draw.
"I did not hear it because I was focusing on the game." Ba told the Evening Chronicle
"If they do that they are really stupid dudes. They have to grow up. People have to man up. There are many people on earth and you have to be responsible."