The police and the FA are investigating after Rio Ferdinand was struck in the face by an object at the end of the Manchester derby.
The Manchester United centre-half was celebrating Robin van Persie's late winner but was left with a gash above his eye after the incident.
No arrests have been made in relation to that incident but separately, Greater Manchester Police have confirmed that nine of the 13 people arrested have now been charged with a variety of offences.
Two men have been charged with pitch encroachment.
Chief Inspector Steve Howard said: "To have just 13 arrests for a crowd of this size and a match of this proportion is a testament to the policing operation we put in place.
"Despite fierce rivalry and high tension there was no major disorder. However, we will continue to investigate the coin throwing incident and are determined to work with the club to bring the perpetrator to justice."
An FA spokesman said: "It is disappointing that after a great game and advert for the Premier League that we are discussing this issue.
"We will work with the clubs and authorities to identify those responsible and support the strongest sanctions available, including life bans.
"We condemn any such acts and it is simply unacceptable that any player is exposed to injury in this way. To witness Rio Ferdinand leaving the field with a cut above his eye to receive treatment is appalling.
"Football in this country has made great progress over recent decades. However, we must maintain the safety and security inside of our stadia and to do this we need to isolate and identify any individuals guilty of offences with strong penalties to act as a deterrent to others."
A Manchester City statement earlier read: "We apologise to Rio. We condemn the actions of the individual concerned.
"We are reviewing the CCTV with the police and our normal security. We will support the police with any investigation and hopefully identify the person as soon as possible."
Ferdinand, who held an object in his hand at the final whistle and proceeded to show it to referee Martin Atkinson before throwing it to the ground, downplayed the incident.
He wrote on Twitter: "What a result, 3 points! Sweet! Whoever threw that coin, what a shot! Can't believe it was a copper 2p....could have at least been a £1 coin!"
But United manager Sir Alex Ferguson condemned the ugly denouement.
"We were very determined to win but it's unfortunate toward the end that the City fan runs on. I don't think you need that," he said.
"The same thing happened at Chelsea which was masked really by all the other things that happened. Two fantastic teams today, I think, and a fantastic game of football and it could do without that."
There were further unsavoury scenes in the Etihad Stadium in the final minutes of the match with one supporter running on to the pitch to confront the players.
Who was the man of the match in the Manchester derby?