Chelsea are facing a probe into the actions of their fans against Malmo in the Europa League.
UEFA could punish the club after away fans were throwing objects at opposing supporters in the stadium.
Chelsea emerged 2-1 winners in the game, but it was not without problems.
Even Eden Hazard was involved in an incident, with a home fan accosting him and demanding that he give his shirt.
It is frustrating for Chelsea, who also had fan trouble in the last round against MOL Vidi, when anti-semitic chants were heard from their section of the crowd.
UEFA has still not decided on a punishment for that incident, with a closed door home game a possible sanction.