Fenerbahce have warned their fans over their conduct after a flare was thrown onto the pitch during their 1-0 Europa League win over BATE Borisov.
The Istanbul giants had to play the match behind closed doors thanks to previous incidents of fan misbehaviour, but supporters were still able to get the firework into the Sukru Saracoglu via the use of a parachute.
And the club have reminded fans that such activities are illegal and could prove detrimental to the team's fortunes.
"This and similar stadium closures due to criminal activity could cause the team harm and are severe enough to interfere with the success of this club," a statement from the Kadikoy outfit read.
Fener will play Viktoria Plzen in the next round of the competition, with the Czechs having knocked out holders Atletico Madrid in the last 32.