Police have arrested a 15-year-old boy in connection with a racist tweet sent to a Manchester United player, understood to be Rio Ferdinand.
The teenager was held last night on suspicion of a racially aggravated public order offence, Greater Manchester Police said.
An investigation was launched after a message was directed at a United player as the fiery encounter between Manchester United and Manchester City was taking place on Sunday lunctime.
The boy has been bailed pending further inquiries.
Ferdinand was at the centre of disgraceful scenes that marred then end of what had been a thrilling Manchester derby. As the defender celebrated his side's last gasp winner courtesy of a Robin van Persie free-kick, he was struck with a 2p coin.
The missile left Ferdinand with a cut above the eye that had to be attended to by medics.
Ferdinand was also the apparent target of a Manchester City fan who entered the pitch and headed towards him. City fan Matthew Stott was restrained by goalkeeper Joe Hart before he could confront Ferdinand. Stott has since apologised for the incident, and seen his season ticket cancelled. He could yet be handed a lifetime ban.
In total, nine people have been charged in connection with the unrest surrounding the Premier League match.