Cardiff City Football Club say they are "aware of allegations" made against their own supporters in Saturday FA Cup tie with Reading.
The club says it will speak to Thames Valley and South Wales Police to "ascertain the facts" surrounding the allegations.
Warnings relating to the alleged incidents were issued via the public address system at Madejski Stadium.
Reading and Cardiff drew 1-1 in their fourth round draw on Saturday.
Callum Paterson opened the scoring for the Bluebirds after only five minutes, only for Reading to equalise three minutes later.
Reading ended the game with ten men after the Royals' Tom McIntyre received a second yellow card with ten minutes to play.
Both sides will find out who they might face in the fifth round when the draw is made on Monday evening.