Guus Hiddink strongly criticised Chelsea supporters who threw objects at Manchester City players during Sunday's FA Cup tie at Stamford Bridge - stating those responsible "should not come into stadiums".
Chelsea eventually ran out 5-1 winners against a youthful City line-up to secure a quarter-final trip to Everton, but there were unsavoury scenes after debutant David Faupala netted a first-half equaliser for the visitors.
After the teenage French striker was joined by his team-mates to celebrate, referee Andre Marriner collected three objects from that corner of the pitch - the first of which appeared to be a coin.
City manager Manuel Pellegrini learnt of the incident during his post-match press conference, saying his players had not informed him afterwards.
But opposite number Hiddink said: "There were coins thrown to the Manchester City players in their celebration - I condemn it strongly.
"Those people [who threw objects] must not come into stadiums."
Following Hiddink's remarks, a Chelsea spokesperson said the club would issue bans and support criminal prosecutions of those responsible.
On Saturday, West Brom midfielder Chris Brunt was struck on his left cheek by a coin thrown from the away end as his team lost 3-1 at Reading in round five.
Thames Valley Police confirmed it was investigating a number of incidents that marred the match at the Madejski Stadium.