Manchester United ejected a fan from Old Trafford during Sunday's Premier League clash with Liverpool over alleged racial abuse.
United say they are investigating the matter as a priority and the PA news agency understands the police have been informed.
A United spokesman said:
We are aware of an incident at yesterday's game where an individual in the home section has allegedly engaged in racial abuse.
It is understood the situation could lead to an indefinite ban.
A Liverpool spokesperson said:
Liverpool Football Club takes all allegations of this manner extremely seriously and will support the strongest possible action being taken against anyone found to be responsible.