Police are investigating after Frank Lampard's 200th Chelsea goal was marred by West Ham supporters throwing coins and hot dogs at the England player.
Former West Ham midfielder Lampard celebrated his headed effort in front of the away fans at Stamford Bridge.
Visiting supporters reacted by throwing objects towards the 34-year-old in a game their team lost 2-0.
"We are investigating instances of coin-throwing," a Met Police spokesperson said.
"There have been no arrests. Inquiries continue."
West Ham are planning to ban any supporters found guilty of throwing coins.
A statement from the London club said: "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, including the possibility of a ban from attending future matches."
The incident could lead the Football Association to take disciplinary action.
There have been previous incidents of coin-throwing during the fixture.
In October 2004, Mateja Kezman was hit by a coin while playing for Chelsea against West Ham in a League Cup tie.