UEFA have opened disciplinary proceedings against Celtic, charging the Glasgow club with "the displaying of a banner of an offensive nature and the setting off of fireworks by supporters".
The case will be heard by the UEFA's control and disciplinary body on January 26.
Some Celtic fans held aloft a two-part banner which insulted UEFA, days after the club were fined about £12,700 for "illicit chanting" involving pro-IRA songs at a Europa League game against Rennes at Celtic Park.
Several flares were also let off and one was thrown onto the pitch-side track as Celtic exited the tournament with a 1-1 draw at the Stadio Friuli last Thursday night.
Celtic have already banned for life one fan who was arrested in Italy over the alleged assault of a club steward, and who they say was one of those responsible for the banner.
Celtic manager Neil Lennon and chief executive Peter Lawwell hit out at the "rogue" element within their support on the day after the game.
The club also vowed to sift through photographic evidence to find those fans responsible for the use of the flares, warning that they will take "appropriate action".
Lawwell said: "It is very frustrating. Those people are not Celtic supporters.
"We will weed them out and these guys will not get back into Celtic Football Club.
"One or two silly little juvenile boys doing funny kids' pranks and stuff and it is bringing the whole of Scottish football down."
Lennon added: "My only surprise is that they got the spelling (on the banner) right.
"I am very disappointed, they have let me down, they have let the board, players and background staff down and 99.9% of the support down."