Chelsea are facing the prospect of a UEFA investigation into alleged antisemitic chanting by their supporters during Thursday's match against Vidi in the Europa League.
The match, which ended 2-2, was marred from the opening minutes by reports on social media of antisemitic chanting coming from the section of Groupama Arena that housed the 1,273 Chelsea supporters who had travelled to Budapest.
Shortly after the final whistle, a Chelsea spokesman issued an official statement condemning the chanting with the strongest possible language.
"Anti-semitism or any other kind of race-related or religious hatred is abhorrent to this club and the overwhelming majority of our fans," the spokesman said. "It has no place at Chelsea or in any of our communities.
"We have stated this loud and clear on many occasions from the owner, the board, coaches and players.
"Any individuals that can't summon the brain power to comprehend this simple message and are found to have shamed the club by using anti-semitic or racist words or actions will face the strongest possible action from the club."
This latest episode comes just five days after Chelsea and Metropolitan Police confirmed that they were investigating claims that Manchester City star Raheem Sterling was racially abused by a Blues supporter during a Premier League game between the two clubs at Stamford Bridge. Four supporters have been suspended from attending games "pending further investigations" into the incident.
In a statement to ESPN, UEFA said: "As is standard procedure, we will be waiting for official reports from the game before deciding if any action/investigation into any alleged misbehaviour should be launched."
A UEFA investigation for the chanting would be particularly embarrassing for Chelsea, who have gone further than any other club in their attempts to eradicate antisemitism from football since launching a targeted campaign at the urging of owner Roman Abramovich in January.
Holocaust survivor Harry Spiro was invited to Cobham to address the Chelsea first-team squad in January, while the club sent a delegation to attend the annual March of the Living at Auschwitz in April.
This was followed in June by an official visit, consisting of 150 supporters and club officials, to the Nazi concentration camp.
Last month Chelsea announced that they will play MLS club New England Revolution in a postseason friendly, branded "Game for Change," as part of their campaign against antisemitism.
Abramovich and Revolution owner Robert Kraft, who are both Jewish, have pledged to donate $1 million (£778,565) to the fight against antisemitism, with all money from ticket sales also going to the cause.