Lazio have denied their fans were responsible for a bar brawl that left one Tottenham Hotspur fan with serious injuries and at least six others needing medical treatment.
Spurs fans are returning home after a clash involving fellow supporters in Rome in the early hours of Thursday.
It happened ahead of Spurs' Europa League match at the Stadio Olimpico.
Witnesses said there was an element of anti-Semitism to the attack, with shouts of "Jews" directed at Tottenham fans. The north London team is known for having a large Jewish fan base.
During the match there were anti-Semitic chants from Lazio fans towards Spurs but there were no reports of violence.
Police in Rome said the homes of more than a dozen people suspected of involvement in the violence were searched.
The brawl in The Drunken Ship - a popular tourist spot in Rome's busy Campo de Fiori - had been blamed on "Ultras", or fanatical fans, although Lazio president Claudio Lotito denied their supporters were responsible.
"When it emerges who was really responsible, some people will be surprised," he said.
"It is all too easy to speak about aggression from people whose faces are covered and say that they are Lazio fans."
In a statement, the club added: "Incidents like what happened last night have nothing to do with football and instead represent pure delinquency, against which the police and magistrates must intervene with every instrument at their disposal."
Tottenham supporters had been urged to use shuttle buses to travel to and from the ground to avoid confrontation with rival supporters.
Dave Webster, a Spurs fan who witnessed the attack in The Drunken Ship from a nearby bar, described a chaotic, violent scene, saying the attack had left some supporters "covered in blood, heads bleeding, arms bleeding".
He told Sky News: "The first thing we heard was broken glass. The main pane of glass at the bar got broken and then all of a sudden we heard women screaming and running out and running away from the bar, and then it was sort of a back-and-forth chase between the two sets of fans and more Italians started pouring in."
Christopher Allen, who suffered injuries to his head and hand as the masked assailants tore through the pub shortly after 1am, said: "The bar was nice and civilised and there was some chanting, then I looked up and saw a big gang of lads outside pulling scarves up over their faces. That is when it all began."
The most seriously injured fan was named by police as Ashley Mills . He was being treated at the city's San Camillo Hospital after reportedly being stabbed, although his injuries are not thought to be life threatening.
Dave Lesley, Stephen Tierney and Christopher Allen were identified as being among the other Britons hurt.
Speaking to ITV4 ahead of last night's 0-0 draw, Spurs boss Andre Villas Boas wished them a "speedy recovery".