Birmingham have vowed to ban for life the supporter who allegedly threw a coin at Blackburn goalkeeper Brad Friedel during Saturday's Barclaycard Premiership match at St Andrews - if they can identify the culprit.
The incident occurred during the second half after Lucas Neill had scored the decisive second goal for Rovers in a 4-0 win.
Friedel handed the coin to referee Graham Barber and he included the incident in his match report to the Football Association who have invited Blues to put forward their observations on the matter.
The club could be in severe trouble as they were warned to their future conduct - as well as being fined £25,000 - following crowd disturbances in last season's derby matches against Aston Villa.
City have condemned the actions on Saturday and are co-operating fully with the Football Association and West Midlands Police over the matter as well as promising to increase CCTV monitoring of the crowd at future matches.
A club statement said: "Birmingham City Football Club does not and will not tolerate the throwing of coins or any other objects by spectators at St Andrews. "Reports that a coin was thrown onto the pitch at Saturday's game are being treated extremely seriously by the club."