Reports from Barcelona suggest a number of Chelsea fans were injured by police before their team's match last night.
A number of videos were published on social media showing police corralling what appear to be Chelsea supporters at Barcelona's Camp Nou video.
One widely circulated video appears to show police using batons around the stadium, as one English bystander calls their behaviour a "disgrace."
Further footage shows Chelsea fans singing "Barcelona, you'll always be Spain", a reference to Catalonia's failed independence bid, and chanting "Espanyol" - the name of Barcelona's city rivals. A number of visiting fans also carried Spanish flags.
Barcelona's local police force, the Mossos d'Esquadra, say they have received no reports of violence.
However Chelsea have asked the club's supporters to contact them about their "experiences."
"We are aware of reports of incidents outside the ground before the game where a number of Chelsea fans were hurt," said the club.
"We ask that our supporters contact us with accounts of their experiences of [their] arrival at the stadium so that we can take this up properly with the authorities."
Barcelona won last's round-of-16 second leg 3-0, meaning Chelsea were eliminated 4-1 on aggregate.