Dozens of refugees hoping to reach Britain scrambled on a cross-channel ferry in northern France, sparking a 12-hour manhunt as police combed the ship to find them, officials said on Sunday. Around 100 refugees broke into the dock area of the port of Calais late on Saturday and dozens managed to get on board the ferry that had just arrived from Dover, England. A total of 63 people were detained, many of whom tried to hide on the Danish-operated DFDS Calais Seaways ferry, regional authorities said. On Sunday morning, firefighters talked down the last group of about a dozen migrants who climbed high above the deck to a catwalk attached to the ship’s funnel. The refugees managed to get aboard the ferry by using a maintenance ladder at high tide, senior regional official Jean-Philippe Vennin said. “Two of the migrants fell into the sea and were quickly rescued by firemen,” he said. Police offloaded vehicles arriving from Britain on the ferry before making a top-to-bottom search of the ship. Those detained were taken to Calais police headquarters, Vennin said. Cross-channel ferry traffic was delayed overnight with at least two forced to stay at sea before being allowed into port. The Calais Seaways was moved overnight so the harbour could resume operations. To reach the port area, “the migrants crossed a pedestrian gangway normally used by employees and I am convinced the place had been cased and that last night’s operation was orchestrated by people smugglers”, harbour master Jean-Marc Puissesseau told reporters after the police search ended. “It’s not normal to have 100 migrants break into a secure area such as a harbour. There must be a failure somewhere,” local mayor Natacha Bouchart said, before blaming police cutbacks. “We must reinforce our police forces on the eve of Brexit which people smugglers exploit in a bid to promote their trafficking,” regional president Xavier Bertrand said on Twitter. Migrants, many from Afghanistan, Iraq and Iran, and smugglers have diversified ways of trying to cross the English Channel. Many still hide in trucks heading to the ports, but more recently others have tried to cross the channel on small vessels and lifeboats stolen from local harbours or acquired by traffickers . On Friday, a French court jailed two Iraqis and an Iranian for organising illegal migrant boat trips to Britain. A 30-year-old Iranian, considered the group leader, received an 18-month sentence, while his two accomplices, aged 39 and 32, were each jailed for a year. Some 500 people tried to cross the channel last year – most of them in November and December, compared with just 13 known attempts in 2017. French interior ministry figures showed that 276 people successfully reached British waters. In December, the UK dispatched a Royal Navy cutter to help coastguard vessels survey the sea that separates France and Britain.