"I did not notice anything, it was probably a misunderstanding which will be clarified by the due authorities. We don't usually have racism-related problems in Portuguese stadiums," Pereira said at a news conference in Manchester on Tuesday ahead of the second leg.
European football's governing body UEFA announced a disciplinary hearing on Tuesday to investigate "improper conduct" by Porto supporters.
"I did not hear any comment which should force the club to apologise. What I often hear are the fans chanting for Hulk, which he, himself, can confirm," the coach added.
Burly Brazilian forward Hulk, the driving force of Porto's recent success, backed up his coach's remarks.
"I did not hear anything; when you are on the pitch you are only focused on the match. In every match we play at home I hear my name and that can cause some misunderstandings, but the fans are rooting for me," Hulk said.
City host Porto in the second leg of the Europa League last 32 tie later on Wednesday.
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