Chelsea are investigating a video circulating on social media in which an individual can be heard using abusive language of a sectarian nature.
The footage was taken during Saturday's 3-0 win over Aston Villa at Stamford Bridge, with visiting midfielder John McGinn heard being subjected to a volley of vile taunts when taking a corner.
The Blues released a statement on Monday asking for information to try and help find the perpetrator, vowing to take the strongest possible action against anyone found guilty.
"We are aware of a video circulating on social media showing an individual using abusive language of a sectarian nature in the crowd at Stamford Bridge on Saturday," the statement read.
"Chelsea Football Club finds all forms of discriminatory behaviour totally unacceptable and we condemn the language used.
"The club is working to identify the person involved and will take the strongest possible action against them. Any supporter who was present in that area of the ground and has information that can assist the club's investigation should contact the club via our discrimination reporting line."