Celtic have issued a statement warning a section of home supporters that their behaviour may lead to the closure of a section of Celtic Park.
Three fireworks were set off during Wednesday's 2-0 Champions League victory over Cliftonville, with UEFA revealing that they have launched an official investigation into the incident.
The Scottish champions have conceded that they have considered closing down Section 111 of the stadium, largely home to a group of supporters known as the Green Brigade, due to safety concerns.
An official club statement released this morning read: "The club is keen to work with spectators in Section 111 to resolve safety concerns. However, it should be understood that failure to stop this unsafe behaviour will require the closure of this area in Celtic Park.
"The Directors and Board of Celtic Football Club consider their responsibilities with regard to Spectator Safety to be of paramount importance.
"We will continue dialogue with representative of fans in this area to resolve these serious safety concerns, however this unsafe behaviour must stop."
Celtic were fined £21,500 by UEFA last season for conduct of their fans during a Europa League match against Udinese.
UEFA have confirmed that they will deal with the Cliftonville incident in a hearing on August 22.
