Greater Manchester Police have arrested a 41-year-old man in connection with allegations of racist abuse during Saturday's Manchester derby at the Etihad Stadium.
A statement from the force read: "At around 6.55pm on Saturday 7 December 2019 police were called to a report of a supporter making alleged racist gestures and sounds towards players during the Manchester City and Manchester United derby.
"A 41-year-old man has been arrested on suspicion of a racially aggravated public order offence and remains in custody for questioning."
Superintendent Chris Hill of the City of Manchester Division added: "I would like to thank the public for their ongoing support with this incident.
"Racism of any kind has no place in football or our society and I hope this arrest shows that we are taking this matter extremely seriously.
"We will continue to work with Manchester City and Manchester United football clubs on this incident and will investigate any other lines of enquiries."
Goals from Marcus Rashford and Anthony Martial helped Manchester United secure a 2-1 win over City but a pulsating match was overshadowed by the alleged incident off the field of play.
During an altercation with a group of City fans, United midfielder Fred appeared to be struck by an object thrown from the crowd as he went to take a corner in the 68th minute. Lighters and a plastic water bottle could be seen on the pitch.
A City fan was also filmed making what appeared to be a racist gesture towards some of the Manchester United players.
More than one United player felt they had been racially abused during the incident, reporting their concerns to City and to referee Anthony Taylor.
Earlier on Sunday, the Football Association confirmed they were investigating the incident.
In a statement released shortly after full time, City said: "The club operates a zero-tolerance policy regarding discrimination of any kind, and anyone found guilty of racial abuse will be banned from the club for life."