The security operation surrounding England's Euro 2016 match against Wales in Lens on Thursday has been increased amid fears of more violence.
Extra British police will be deployed ahead of the next round of Group B matches.
Concerns have been raised about the security of fans, with Russia playing Slovakia in Lille -- just 23 miles away -- on Wednesday.
UEFA has handed Russia a suspended disqualification from Euro 2016 following the crowd disturbances at the opening group game against England in Marseille on Saturday.
A group of 150 Russian hooligans involved in the Marseille trouble and were described by the French authorities as "hyper violent," are feared to still be at large.
Trouble also flared in the city in the days before the game, and the Football Association has also been warned that England could be kicked out if there are further disturbances.
FA chairman Greg Dyke has voiced "serious concerns" about security.
Answering an urgent question in the Commons on Tuesday, Home Secretary Theresa May said British police officers known as "spotters," trained to identify troublemakers, have been sent to France.
British officers trained in public order will also be deployed but May said that, for "operational reasons," she would not reveal how many officers were being sent across the Channel.
She called the violence involving England supporters "deeply disturbing" but blamed Russian fans for instigating much of the worst of it.
British police are searching for 48 England fans involved in fighting in Marseille in order to ban them from attending matches at home.
Mark Roberts, the head of football policing in Britain, told The Associated Press that his team had been working with French investigators to find the suspects.
He said: "There are currently 48 people we have images of, and we will be seeking banning orders on them once we have identified them and they return to the UK.
"We are obviously concerned [about Lille]. What we saw in Marseille was appalling violence.
"It was concerted, and largely came from people who came with the sole intent of injuring others. So we have to be concerned."
Fabienne Buccio, the prefect of the Pas-de-Calais region, said Lens would be "in lockdown by the police".
She added: "We will have a strong police presence with more than 1,200 police officers present in Lens and you can add 1,200 more with the private security that will be mobilised that day.
"We have strengthened the safety systems inside the stadium. They will be present in the stands ready in order to intervene quickly in the stadium if there are clashes between supporters."
The developments come as the first England fan to appear in a UK court over the trouble in France was handed a five-year football banning order.
Six British fans were jailed for between one and three months on Monday for their part in the Marseille violence.
Meanwhile, a bus carrying 29 Russia supporters was stopped by police after leaving a hotel near the town of Mandelieu-La Napoule, on the Cote d'Azur, on Tuesday, a local official confirmed.
Prefecture communications chief Ariane Parachini said police stopped the fans to see whether any hooligans were among them.