The president of European football's governing body UEFA, Michel Platini, wants to know why guidelines on dealing with racism were not followed during Thursday's Champions League match in Moscow.
Manchester City beat CSKA Moscow 2-1 in a game marred by racist chanting reported to the referee by City's Ivorian midfielder Yaya Toure.
Platini wants an internal inquiry on why UEFA guidelines, which allow a referee to suspend or abandon a match in the event of racist chants, were not adhered to.
UEFA has already charged CSKA Moscow over their fans' behaviour and a report into the incident is expected before the end of the month.
But Platini, who has made the fight against racism in the game a major priority, wants to know why the referee allowed play to continue.
Under UEFA's anti-racism protocol, in the event of racist chants from fans, the referee should halt the match and issue a call over the public address system for the chants to stop.
If the chanting persists, he should suspend the game and take the players off the field before making a second announcement.
If the chanting resumes once play is restarted, he is expected to abandon the game.
Toure later said he did not exclude the possibilty of black players boycotting the 2018 World Cup in Russia as a result of their treatment at the hands of Russian fans.
