UEFA has opened disciplinary proceedings against Chelsea on a charge of racist behaviour relating to antisemitic chants by their supporters.
Reports on social media said antisemitic chanting had come from the section of Groupama Arena housing travelling Chelsea fans at Vidi game.
UEFA have opened disciplinary proceedings against Frankfurt after their fans caused trouble in Rome, but have not done so with Lazio.
Arsenal will face Belarusian side Bate Borisov in the Europa League round of 32, while Chelsea have been drawn against Sweden's Malmo.
AC Milan must break even on football-related business in June 2021 or face a ban from UEFA competitions for a season.
Frankfurt were in the city to play Lazio in the Europa League, with the Bundesliga side winning 2-1.
Saka made his first start for the Gunners on the left wing in a 1-0 Europa League win against Qarabag.
Unai Emery used a blend of youngsters and players returning from injury vs. Qarabag. In an otherwise dull match, Eddie Nketiah, 19, caught the eye.
Olympiakos pulled off a stunning 3-1 Europa League win over AC Milan that put them into the round of 32 and sent the Italians crashing out.
Alexandre Lacazette's first-half goal gave Arsenal a 1-0 win over FK Qarabag in Europa League Group E action on Thursday.
Chelsea are facing the prospect of a UEFA investigation into alleged antisemitic chanting by supporters during Thursday's match against Vidi.
Chelsea fell behind in their Europa League trip to Vidi, but Olivier Giroud came off the bench to score an exquisite free kick and salvage a draw.
Table-toppers Chelsea drew 2-2 at Vidi in their final Group L in the Europa League on Thursday.
Arsenal midfielder Ainsley Maitland-Niles has joined Raheem Sterling in speaking up against racism.
The last 32 of the Europa League are confirmed. Here's when the draw for the round of 32 of the Europa League will happen and the other key dates.
After Chelsea's 4-0 win against PAOK, Sarri was qualified in his praise of Hudson-Odoi, reminding him where he expects him to improve.
Jesus Corona kept up his form in Champions League play with yet another goal. Here's how Mexican players fared this week in European competition.
Smith Rowe scored the opening goal of a 3-0 win and was one of several youngsters who impressed for Arsenal.
It was a good day for Chelsea all-round as Cesc Fabregas turned back the clock, Olivier Giroud scored twice and teen Callum Hudson-Odoi impressed.
AC Milan were given a helping hand as they survived a big scare before beating Dudelange, while Celtic earned a big win against Rosenborg.
Chelsea made it five wins in five tries in the Europa League with a convincing 4-0 win against PAOK at Stamford Bridge on Thursday.
Unai Emery gave the kids a chance vs. Vorskla and they didn't disappoint: Emile Smith Rowe and Joe Willock scoring and three others making debuts.
AC Milan came from behind before stepping on the gas to pull away from F91 Dudelange for a 5-2 Europa League win on Thursday.