UEFA is to hold an investigation into the actions of both Marseille and Manchester United fans after the teams' 0-0 draw in the Champions League at the Stade Velodrome on Wednesday.
It is reported that seven United supporters were arrested on the night, with four of them said to have been responsible for lighting a flare in the away section of the ground.
Chelsea fans found guilty of a similar offence when the Blues travelled to Marseille during this season's group stage were handed six-month prison sentences.
Marseille fans will also be the subject of a separate investigation after apparent attempts to distract United players using laser pens. Lyon were fined €3,200 for "incidents of an unsporting nature" after using lasers to distract Cristiano Ronaldo during his time at Manchester United three years ago.
UEFA has confirmed its disciplinary panel will hear the cases on March 17.