UEFA has opened disciplinary proceedings against St Etienne in the wake of incidents involving the French club's supporters during Thursday's Europa League tie against Manchester United at Old Trafford.
Les Verts suffered a 3-0 defeat in the first leg of their round-of-32 tie against United, who visit the Stade Geoffroy-Guichard for the return fixture next Wednesday.
But the Ligue 1 side could now be hit with a financial penalty from European football's governing body after their supporters were charged with setting off fireworks, throwing objects and improper conduct during the United game.
A statement from UEFA reads: "Disciplinary proceedings have been opened against AS Saint-Etienne due to the behaviour of their supporters during their UEFA Europa League Round of 32 match against Manchester United FC on 16 February 2017 at Old Trafford.
"The following proceedings have been opened against AS Saint-Etienne for the following infringements: Setting off of firework - Art. 16 (2) of the UEFA Disciplinary Regulations (DR); Throwing of objects - Art. 16 (2) DR; Improper conduct of supporters - Art. 16 (2) DR."
The early stages of the game were marred by the setting off of a number of flares in the away section, despite the deployment of pyrotechnic sniffer dogs prior to the fixture.
The UEFA Control, Ethics and Disciplinary Board will meet on March 23 to deal with the case.