Uefa are expected to take a tough line following the violent scenes in the Olympic Stadium in Rome - and that could mean bad news for both Manchester United and Roma.

Michel Platini, the new Uefa president, last week wrote to the heads of all the European national associations calling for a 'zero tolerance' approach to football-related violence.

In his letter, Platini said: "Violence on the field, in the stands and outside stadiums is poisoning football. While taking care to respect their independence, I have asked our disciplinary bodies to apply our regulations as strictly as possible. We need a policy of zero tolerance against violence and racism."

Uefa have launched an investigation into the crowd trouble and will announce any disciplinary proceedings after the Easter weekend.

Disciplinary action would be a real concern for United as it is less than two weeks since they were fined £6,300 by Uefa for trouble involving their fans during the first leg of their last-16 tie against Lille. The onus for security rests mainly with the home club however, and Roma can also expect to be charged.

A statement read: "Uefa have opened an investigation into the incidents that occurred at the UCL match AS Roma-Manchester United FC. Uefa is currently gathering evidence and will be studying the official reports of the referee, delegate and security officer in detail before announcing any further action."

On the subject of policing, William Gaillard, the Uefa communications director, said the organisation was in favour of a low-key approach but had the power to influence security arrangements. "In Italy the police are responsible for public order inside stadiums," Gaillard said. "Stewards are not responsible for security - they just show you to your seat.

"We are definitely in favour of a soft policing approach and the use of stewards rather than the involvement of riot police. But we cannot tell the Italian authorities, or indeed those of any other country, how to apply law and order."

Meanwhile, former referee Anders Frisk believes police aggression made a tense situation much worse in last night's match between Manchester United and Roma.

Frisk - who abandoned a game between Roma and Dynamo Kiev in 2004 after being struck by a missile - believes the police's heavy-handed tactics were largely to blame for the ugly scenes which marred the game.

"The approach from the Italian police - my feeling was that they were very close to the United supporters," Frisk said. "What caused it was something that had been thrown. The Italian police reacted very, very aggressively towards one or two incidents. This is what caused everything to catch fire."

Frisk also claimed that lax security on the way into the ground was another factor: "When I went through the gates I was not searched at all, and of course if you do not search the people they will bring in bottles and things to throw at each other - that was a major mistake."