Manchester United are reviewing CCTV footage to identify fans who threw objects onto the pitch after their 1-0 loss to Atletico Madrid.
Atletico boss Diego Simeone was pelted with missiles including bottles after the final whistle at OId Trafford.
Uefa is waiting for reports from match observers before deciding whether to charge the club.
Throwing objects onto the field of play is against ground regulations and subject to a three year ban.
Ralf Rangnick's side were knocked out the Champions League following a 2-1 defeat on aggregate to the Spanish club.
The result thwarted United's hopes of ending a five-year trophy drought, meaning they are on their longest run without silverware since the period between FA Cup wins in 1977 and 1983.
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