A man has been arrested after a video posted on social media showed a supporter making racist gestures at the Manchester City v Manchester United match at the Etihad Stadium yesterday.
The 41-year-old is being held on suspicion of a racially aggravated public order and remains in custody for questioning.
It is understood that United reported that more than one of their players felt they had abuse of a racist nature aimed at them.
There were also reports of missiles being thrown as tempers boiled over in the stands, with Fred appearing to be hit by an object hurled from the crowd as the visitors prepared to take a corner.
Manager Ole Gunnar Solskjaer said: "Fred and Jesse (Lingard) were in the corner, taking a corner, and I've seen the video, heard from the boys.
"We keep talking about it every bloody week.
"But he's been caught on camera. He should, in my opinion, never be allowed into a football ground again and I've seen the video. Unacceptable.
"So I am sure that City and the authorities will deal with it.
"As I said, we keep talking about it every week and it doesn't stop unless it'll have consequences."
Superintendent Chris Hill of the City of Manchester Division said: