Celtic - second in Group G two points behind leaders Barcelona after their 2-1 win over the Spanish side last week - could book their spot in the Champions League last 16 with a win in the Portuguese capital on Tuesday evening.
Benfica's hopes would be damaged if they are forced to play the match in front of an empty stadium in a match they need to win with Celtic three points ahead of them in the section.
They have already been fined 40,000 Euros for throwing flares and fireworks during their home match with Barca last month.
Their fans were guilty of tossing more flares during the 2-0 home win over Spartak Moscow last week.
UEFA are set to decide Benfica's punishment before the end of the week.
- Sports & Recreation