Manchester United have promised to hand out indefinite bans to any supporter found guilty of throwing missiles at last night's Carling Cup semi-final.
It is believed Greater Manchester Police have already arrested the fan who threw a bottle of cider at Craig Bellamy as the Manchester City winger was about to take a corner during the second half of United's highly-charged 3-1 win.
The hunt is now on for the coin-thrower who struck Bellamy on the back of the head at around the same time.
CCTV footage will be studied in an effort to identify the hooligan who caused the most serious incident of the evening.
United expect GMP to request immediate banning orders for any supporter convicted that would be in place by United's next home game against Portsmouth on February 6.
"Once we have the referee's report and asked for a report from the club itself we can establish what, if any, action is merited," said an FA spokesman.