Chelsea back criminal prosecution against fan 'who made racist gesture' to Manchester United's Danny Welbeck The club statement said: "Chelsea Football Club can confirm we are investigating an incident involving a member of the crowd at last night's game against Manchester United. The club will be examining all available footage and asks anyone who can identify the individual to contact the club. Having banned a supporter for life in March for racially abusing former Chelsea player Didier Drogba, it is anticipated that a similar sanction will be applied should the man involved in Wednesday's incident be identified. Meanwhile, Chelsea are also investigating a number of incidents which occurred during the dramatic 5-4 victory against United, including allegations of missiles being thrown and a supporter entering the playing from the section housing the visiting supporters. Although the Football Association is understood not to be launching its own investigation into the incidents, Chelsea have begun an internal probe. The events of Wednesday night were the second incidents of apparent crowd disorder in the space of four days, with a steward forced to undergo hospital treatment after being knocked the ground following United's winning goal in Sunday's Premier League fixture. Chelsea defender Gary Cahill insists Roberto di Matteo's players will not be distracted by the off-field issues which have the club recently. "It's important that we don't let anything affect us and we showed that won't happen," Cahill said. Whatever is going on off the pitch, players relish playing football. Although we were very unfortunate (against United) on Sunday, it was important that we got back to winning ways after two sticky results, especially against Manchester United.