Paris St Germain are set to be punished by UEFA for their fans setting off flares and other offences in their 2-1 defeat at home to Real Madrid in the Champions League on Tuesday, which saw the French side exit the competition 5-2 on aggregate.
A statement on the European football governing body's website (www.uefa.com) said it was investigating the Ligue 1 leaders on four counts of violating its disciplinary regulations, for setting off fireworks, pointing a laser, blocking stairways and "insufficient organisation".
"Disciplinary proceedings have been opened following the UEFA Champions League Round of 16 match between Paris Saint-Germain and Real Madrid CF (1-2), played on 6 March in France," said the statement.
"The case will be dealt with by the UEFA Control, Ethics and Disciplinary Body on 22 March."
German referee Felix Brych had to stop the game on two occasions due to the excessive amount of smoke on the pitch from the flares, harming the visibility of officials and players.
PSG's 'Ultra' supporters also set off flares near to the hotel Real were staying at in the French capital the night before the game, prompting a complaint from the Spanish side to UEFA.
UEFA said it was also investigating Swiss champions Basel after their visiting supporters set off flares in their last-16 second leg game at Manchester City on Wednesday.
UEFA's regulations state a club will be fined 500 euros for every flare set off during a game for first time offenders, then 750 euros for every other flare for repeat offenders.