A man has been arrested on suspicion of making racist comments during Manchester United's Premier League win over Crystal Palace.
The 56-year-old was arrested at Old Trafford on Sunday on suspicion of a racially aggravated public order offence and remains in custody.
Supt Caroline Hemingway said: "This type of behaviour is utterly unacceptable."
United won the game 1-0 thanks to a 77th minute goal from midfielder Fred.
Supt Hemingway said the force worked "closely with Manchester United to promote good behaviour at matches and to identify anyone who commits a criminal offence".