Chelsea and the Metropolitan Police are investigating whether Raheem Sterling was racially abused during the Blues' 2-0 win over Manchester City on Saturday.
Television footage appeared to show spectators in the front row at Stamford Bridge berating the City winger, prompting allegations that some of the words were racially motivated.
Chelsea have vowed to take the "strongest possible action where necessary", while a police statement confirmed the widely circulated video was being reviewed, although no arrests have yet been made.
"We are aware of a video circulating online in which it is claimed racial abuse was allegedly directed at a player at a Chelsea v Manchester City game at Stamford Bridge on Saturday 8 December," read the statement.
"We will review the footage to determine whether any offences have been committed."