Aberdeen FC have said the club is “deeply disappointed” by the behaviour of a small minority of supporters during their 2-1 defeat by Eintracht Frankfurt in Germany.
A supporter was arrested in connection with an alleged pyrotechnic incident during the Europa Conference League game.
The Dons lost their opening game in Group G 2-1 against the Bundesliga side.
Following Dante Polvara’s first-half equalising goal for the Dons, there were reports that a lit pyrotechnic was thrown into the home end.
A statement from Frankfurt Police read: “During the first half of the game, one of the away fans threw a burning pyrotechnic object into the neighboring home fan block.
“Fortunately, no one was injured.
“We caught the crime on video and arrested the suspect.”
Aberdeen FC have vowed to fully cooperate with any investigation into the incident.
A club statement read: “The club is deeply disappointed by the actions of a small minority of supporters during this evening’s match which threatens to tarnish the good reputation of Aberdeen FC and the vast majority of Dons supporters.
“The club will fully co-operate with UEFA and the relevant authorities during the course of any investigations.”
Around 2,900 Aberdeen fans were at the Deutsche Bank Park to cheer on the Dons as they played in the group-stage of a European competition for the first time since 2007.
The Germans took the lead when Omar Marmoush converted from the penalty spot inside 11 minutes.
Polvara finished off a clinical counter-attack in the 22nd minute to restore parity but Robin Koch headed home what proved to be the winner in the 61st minute.
