UEFA has opened disciplinary proceedings against Porto for "improper conduct” of fans during the Europa League match against Manchester City.The Premier League leaders made an official complaint to the European governing body following their first-leg win in Portugal on February 16.City alleged there had been racial abuse towards striker Mario Balotelli and midfielder Yaya Toure.A statement from Uefa said that it would deal with the case on March 29."What I have to say on that, is that normally in our league and our stadiums we don’t have problems like that regarding racism”Uefa had been waiting to see the report from its match delegate before deciding whether to launch a full investigation.If found guilty, Porto face punishment ranging from playing a match behind closed doors to being banned from a Uefa competition, plus they may be fined.