Mamelodi Sundowns have apologised to Al Ahly after the abuse directed at coach Pitso Mosimane.
Mosimane revealed on Saturday that he was subjected to insults from Sundowns supporters before their second-leg encounter.
The Brazilians have now issued an apology to the Red Devils and revealed an investigation will take place to find the supporters responsible.
"Mamelodi Sundowns observed behavior and conduct from some of its supporters before its match with Al Ahly which is unacceptable and improper and does not reflect the integrity, respect, compassion, and other values that we uphold.
"We received complaints by supporters of improper conduct and insults but Mamelodi Sundowns supporters should under no circumstances, disrespect, insult or behave in the manner they did and must at all times stay true to our values and principles.
"We therefore want to apologize to Al Ahly and those associated with the Club.
"Mamelodi Sundowns will institute an investigation and appropriate action will be taken against those supporters whose conduct was improper and contrary to the values and principles that we adhere to.
"We remain dedicated to maintaining the good relations, mutual respect and mutual commitment that exists between the leaders of our two Clubs and all our stakeholders."
See where Al Ahly sit among the top-ranked sides in Africa in the gallery below.