The four men, all Albanians aged 20 to 30, were arrested on Thursday evening in a dockside freight container in Brevik, on the south coast of Norway, before it was due to be loaded onto a cargo ship bound for Immingham, Lincolnshire.

None of the four men are believed to be key figures in the smuggling network, police said. They each had sleeping bags with them as they prepared for the 25-hour journey.

After an arrest described as undramatic, they were held on charges of violating Norway’s Immigration Act.

Prosecutor Odd Skei Kostveit has called for the four men to be detained for four weeks and then deported.

Norwegian police said they have long suspected the existence of a smuggling ring that uses containers on DFDS Seaways’ shipping routes to ferry passengers illegally between the two towns in Norway and England.

“We’ve had this human smuggling operation under observation since 2010. British port authorities and police have concluded that people have been smuggled from Brevik to Immingham without being caught. This route is known to us,” said Kostveit.

Police said their investigations had revealed that migrant Albanians were being brought to Brevik from Sweden.

“The people who drive them here help them get settled before driving back [to Sweden]. The ones heading to England have to pay quite a lot for the trip,” said Kostveit.

He added that police in Denmark had also arrested two Albanians in 2010 on charges of smuggling their compatriots into the UK.  

“Since then we have also arrested a couple of others in containers, and we got back a couple who didn’t manage to get off the ferry in England,” said Kostveit.

Norwegian police said the four men arrested on Thursday were most likely known to police in the UK, as Albanians expelled from Britain often tried to make their way back into the country.

“They have to find a way to get in unnoticed. This is one of several ferry routes, but it is one of the shortest,” said Kostveit.

“Esbjerg in Denmark also has a big problem with this. Norway has become a transit country for a human trafficking route.

“Heading to England involves crossing the Schengen border,” he added, referring to a 26-country European border agreement.

Norway and Sweden are both signatories of the Schengen Agreement, but the United Kingdom is not, meaning would-be illegal immigrants must find a way past the border controls now absent in much of the rest of Europe.

The prosecutor added that the police have a good relationship with the port terminal and the ferry operator.

“A number of surveillance measures have been put in place, as well as increased checks on the containers before they’re driven on board. The more people we catch, the more information we get,” said Kostveit.