UEFA have charged FC Basel after the club's supporters set off fireworks during Tuesday's 3-0 defeat against Manchester United at Old Trafford, BBC Sport have reported.
The Swiss champions were convincingly beaten by the home side, with goals from Marouane Fellaini, Marcus Rashford and Romelu Lukaku.
And things have got worse following confirmation that they have been hit by a charge from European football’s governing body.
A statement on the UEFA website said: "Disciplinary proceedings have been opened following the UEFA Champions League group stage match between Manchester United FC and FC Basel 1893 (3-0), played on 12 September in England.
"Charges against FC Basel 1893: Setting off fireworks – Art. 16 (2) of the UEFA Disciplinary Regulations (DR).
"This case will be dealt with by the UEFA Control, Ethics and Disciplinary Body on 19 October."
Basel are not the only side to have found themselves in trouble following the opening night of Champions League fixtures. Celtic and Paris Saint-Germain have also been charged over incidents during the Ligue 1 club's 5-0 victory in Glasgow.
In a similar case to that of Basel's, French club St Etienne were fined 50,000 euros in March when fans set off fireworks and threw objects in their Europa League last-32 clash at Old Trafford.