Greater Manchester Police have confirmed that a fan was arrested at the Etihad Stadium on Sunday, after racist chanting was heard during the Manchester derby.
Police acted during Manchester United's 3-2 victory against arch-rivals Manchester City, a result that moved Sir Alex Ferguson's side six points clear at the top of the table.
"Man arrested inside stadium on suspicion of committing a racially aggravated public order offence after officers hear racist chanting," the force posted on Twitter.
It was the second arrest of the day at the ground, as officers also stopped a fan on suspicion of ticket touting prior to kick-off.
There was further trouble inside the ground close to full-time, as Rio Ferdinand appeared to be struck by a coin thrown from the crowd while celebrating Robin van Persie's winner, as another fan also encroached on the pitch to confront the United defender.