Chelsea are investigating claims that striker Daniel Sturridge was racially abused by one of the club's own fans.
Sturridge, who is set to make his England debut on Tuesday against Sweden, was reportedly the subject of taunts from a Chelsea supporter during the UEFA Champions League tie at Genk last month.
The club's chief executive, Ron Gourlay, received the complaint via email from another Chelsea fan who had been sitting nearby the supporter who allegedly made the racist comment towards Sturridge.
A Chelsea spokesman told The Guardian: "We have had a new complaint from a fan that we are taking very seriously indeed.
"We are carrying out an immediate investigation led by our head of security that is likely to involve the police as well.
"We will not tolerate any form of racism and have encouraged our supporters to help identify those responsible and we will track them down."