West Ham United's owners have written a letter to supporters telling them to report cases of racist abuse among Hammers fans following the anti-Semitic chants during their 3-1 loss at Tottenham Hotspur on Sunday. A small number of West Ham fans allegedly chanted "Viva Lazio" and "Can we stab you every week?" in relation to an attack on Tottenham fans in Rome ahead of a Europa League match with Lazio last week.
There were also reports of fans chanting "Adolf Hitler, he's coming for you", and hissing, mimicking the gassing of Jews during the Holocaust.
"Saturday's match with Chelsea promises to be thrilling affair and we know we can count on all of you to provide the customary passionate backing for the team that we have witnessed in every game since we arrived at the club," it said.
"That is why we were disappointed to read about the actions of the small section of fans that let the club down during last Sunday's game at Tottenham Hotspur.
"We were not only disappointed because they reflected badly on our club, but they misrepresented the tens of thousands of outstanding supporters who follow the team home and away throughout the season. "In the rare case that you do see or hear anything inappropriate, there are a number of ways you can report the matter."
The club have already banned a season ticket holder in relation to the incidents at Spurs. Five fans were arrested during the game and two cautioned by police for "racially aggravated gesturing", the club said on Monday. Media reports said the gestures were Nazi salutes. West Ham's Israeli midfielder Yossi Benayoun said he had heard the chants and manager Sam Allardyce said he was disappointed after learning what had happened. The Football Association is also investigating the reports.