West Ham's owners have warned fans that the club with not tolerate any kind of racist chanting, ahead of tonight's match against Tottenham.
The FA are still investigating chants from the reverse fixture in November, when Hammers fans were heard chanting about Hitler and making hissing sounds to imitate the sound of Nazi gas chambers.
Spurs are known for their traditional links to the Jewish community.
In a statement, West Ham owners David Gold and David Sullivan said: "There are occasions when individuals still act in an inappropriate way and we have a simple zero-tolerance policy when those isolated incidents do occur at matches at the Boleyn Ground.
"Working with the Metropolitan Police, we will pursue the harshest sanctions against any individual who goes against what we stand for as a club, and in the rare case that you do see or hear anything you think is unacceptable, there are a number of ways you can report the matter."
After November's match, which Spurs won 3-1, West Ham's Israeli international Yossi Benayoun spoke of his disappointment and embarrassment at hearing anti-Semitic abuse by some of the club's fans towards Tottenham's supporters.
One fan was banned from the stadium.