Uefa has announced it will investigate the crowd trouble during Manchester United's Champions League match in Rome.
Baton-wielding riot police laid into United fans in the Stadio Olimpico after trouble broke out during the match.
Italian police clash with Manchester United fans during their Champion's League quarter-finals first leg soccer match at the Stadio Olimpico, Rome last night
Uefa communications director William Gaillard, who was in the stadium, said: "I only saw glimpses of what went on, I saw some missiles flying and the police charging. We will be waiting for the delegate's report, and the control and disciplinary body will be looking at the television images to see the dynamics of what actually happened."
Roma could face action if they are judged to have failed in their security arrangements.
But if United fans are found to have a played a significant role in provoking the police's reaction, they could be in trouble - especially as only last month they were fined for the misbehaviour of some supporters in Lens during the Lille game.
Trouble flared after rival fans surged towards a barrier separating them and missiles were thrown. Police officers were seen repeatedly striking United supporters, including at least two as they lay on the floor.
The Independent Manchester United Supporters' Association later said it is compiling a dossier to submit to Uefa.