Police are investigating several ugly incidents that took place during Chelsea's 2-0 derby victory over West Ham at Stamford Bridge.
Sunday's clash was decided by goals for Frank Lampard and Eden Hazard - but focus has since fallen on the behaviour of fans during the game.
Police are in the process of investigating what appeared to be a hail of coins thrown in Lampard's direction as he celebrated the opener - and have already made two arrests regarding alleged racially aggravated public order offences.
A Met Police spokesperson said: "We are investigating instances of coin-throwing at Chelsea versus West Ham on Sunday, March 17. There have been no arrests. Inquiries continue."
A West Ham statement read: "West Ham United will be working with Chelsea to investigate the reports of missile throwing during Sunday's game at Stamford Bridge.
"Any individual found to have acted in an inappropriate way will have to face the consequences of their actions."
The fixture has a history of coin-throwing incidents; Mateja Kezman was struck by a coin in October 2004 while playing for Chelsea against West Ham in a League Cup tie.