Porto deny allegations that Manchester City players were racially abused by home fans during Thursday night's Europa League tie at the Estadio do Dragao.
UEFA will wait to see the report from their match delegate Joti Chatzialexiou before deciding whether to launch a full investigation.
Porto suggested that chants dedicated to their striker Hulk, or even City's Sergio 'Kun' Aguero, were maybe mistaken for racist noises.
"Nothing abnormal happened, no-one noticed anything strange, not even the UEFA delegates that worked closely with Porto during the match. We are very proud of having a multi-racial team. Porto players have never felt the slightest hint of racism and we were very surprised with the accusations.""Kun, Kun, Kun, Hulk, Hulk, Hulk, can be easily confused with racist chants," said spokesman Rui Cerqueira.