UEFA has charged Benfica after their supporters set off fireworks during the 2-0 defeat against Manchester United at Old Trafford on Tuesday.
United inflicted a fourth straight Champions League defeat on Benfica to leave the Portuguese club bottom of Group A without a point.
And Rui Vitoria's side could face punishment from UEFA following their supporters' use of fireworks at Old Trafford, with the governing body set to make a decision on Nov. 16.
A UEFA statement read: "Disciplinary proceedings have been opened following the UEFA Champions League group stage match between Manchester United FC and SL Benfica (2-0), played on Oct.