With full co-operation from the Premier League club, Northumbria Police are assessing the situation in a move that has pleased Show Racism the Red Card chief executive Ged Grebbby
Police are investigating an image that appears to show a Sunderland supporter directing a monkey gesture towards West Brom striker Romelu Lukaku.
The incident occurred after the Chelsea loanee found the back of the net to give put his side 3-1 in front, before eventually running out 4-2 winners, against the Black Cats on Saturday.
Northumbria Police have confirmed they are looking into the gesture, with Sunderland fully co-operating.
A club spokeswoman said: “Sunderland operates a policy of zero tolerance towards racism and anti-social behaviour of an kind and naturally we will co-operate with the police fully investigating any such incidents."
Ged Grebby, chief executive of anti-racism charity Show Racism the Red Card, has welcomed the investigation.