Gardai and officials from Limerick FC and Thomond Park, which staged Sunday night's game, have moved swiftly after City defender Gael Clichy revealed that an object had been hurled on to the playing surface during his side's 4-0 victory.
A statement released on behalf of Limerick and Thomond Park Stadium on Monday evening said: "Limerick FC officials met with Thomond Park officials and local Gardai this afternoon to continue attempts to identify a person that threw an offensive object on to the playing field during the friendly game on Sunday night, August 5."
It went on: "An incident of this nature is completely unacceptable and is fully condemned by Limerick FC and Thomond Park. CCTV footage is still being analysed and when the offending party is identified, appropriate action will be taken.
"It is deeply upsetting that the actions of one individual have soured the experience for all those in attendance."
An investigation was launched after France international Clichy drew attention to the issue via his Twitter account.
He tweeted: "How sad to see 'bananas thrown on the pitch' tonight... Knowing people around the world need food. #nowordsforthis."
It is understood Clichy did not inform City officials after the game, and that no complaint was made by the Barclays Premier League club.
However, the organisers reacted immediately and vowed to deal firmly with the perpetrator.
An earlier statement said: "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. All those involved with the friendly game fully condemn all forms of unacceptable behaviour of this nature."