ZAGREB (Reuters) – Dinamo Zagreb midfielder Arijan Ademi failed a drug test after their Champions League match against Arsenal last month and is under investigation by UEFA, the club said on Wednesday.

“We have been informed about the results of the drug test and that our player Arijan Ademi tested positive,” the Croatian title holders said on their website.

“UEFA has opened a proceeding against him and in compliance with the football governing body’s rules, Dinamo cannot comment until the disciplinary procedure is over and the B sample result is announced.”

Dinamo beat Arsenal 2-1 at home in their Group F opener on Sept. 16 before losing 5-0 at Bayern Munich two weeks later.

They are third in the section with three points from two games. Bayern lead the standings with a maximum six points while Olympiakos Piraeus are ahead of Dinamo on goal difference.

Dinamo released a statement to say club officials were “surprised” with Ademi’s failed drugs test.

“He had been tested six times in the past year and the results always came back negative.”

(Writing by Zoran Milosavljevic in Belgrade, editing by Pritha Sarkar)