Dinamo Zagreb midfielder Arijan Ademi has returned a positive drugs test for his 'B' sample, the Croatia club have confirmed.
Ademi initially failed a routine drugs test after Dinamo's unexpected 2-1 Champions League Group F victory over Arsenal on September 16 in Zagreb, where he had played the whole 90 minutes.
As the 'B' sample is also now proving positive, Macedonia international Ademi - who also played in the 5-0 defeat away to Bayern Munich on September 29 - could face a suspension from UEFA.
A statement from Dinamo Zagreb read: "The 'B' test urine sample taken from Arijan Ademi after the Champions League first-round match against Arsenal has also tested positive.
"The UEFA Disciplinary Commission will decide on the case at its meeting on October 27, after which we will know more information.
"According to the rules of UEFA, Dinamo players should not make any comment until the disciplinary process is complete.
"When we have more information, we will inform fans and the public through the official club website."
The result of the match against Arsenal is not expected to be impacted by the result, while there are no sanctions against clubs from the governing body unless two or more players fail doping tests.
Arsenal manager Arsene Wenger, though, has been left less than impressed by the whole saga.
Speaking ahead of Tuesday night's Champions League match against Bayern Munich, he said: ''When I saw that the players of Zagreb were doped... when you don't play at your best and your opponent is doped, it is difficult."
Wenger continued: ''Well the rules are the rules and I cannot change that. I don't think the result is really under any threat.
''We have to wait now to wait and see what comes out of the second (doping) control (test).''
