UEFA "is aware that incidents of a racist nature" took place during the PFC CSKA Sofia-Liverpool FC tie on Wednesday.
"UEFA is aware that incidents of a racist nature have taken place at the CSKA Sofia-Liverpool match, and is waiting to receive the official delegate's report. At present, it seems probable that, should a disciplinary case be opened, it would be dealt with by the UEFA Control and Disciplinary Body at their next meeting scheduled for 18 August."
Holders Liverpool won the game 3-1 to boost their chances of reaching the group stage. The second leg will take place at Anfield on 23 August.