Some 21 stowaway migrants claiming to be from Albania have been taken from a cargo ship in Great Yarmouth.
The migrants - 19 men and two children - were discovered by crew members aboard the Rotra Mare which was detained five miles off the coast as a multi-agency operation swung into action.
In a statement Border Force said its officers worked with the Coastguard, the Great Yarmouth Port Harbour Master, Norfolk Constabulary and the vessel's agent to resolve the situation.
It added: "A total of 21 stowaways - 19 men and two minors - have been identified.
"They have all presented themselves as Albanian nationals and will be dealt with in line with the immigration rules."
The Rotra Mare was transporting wind turbines from Spain when crew members found suspected illegal immigrants who may have boarded in Bilbao.
It is understood the drama unfolded in the early hours of Tuesday, September 24, and that the boat was held offshore while the incident was dealt with.
A spokesman from Peel Ports confirmed that stowaways had been identified on board the Rotra Mare and that it was working closely with the relevant authorities dealing with the matter.
The vessel was due to arrive in Great Yarmouth from Bilbao at midday on Monday, but was finally allowed to dock in port on Wednesday afternoon.
The Netherlands-registered container/cargo ship was built in 2008.
Vehicles belonging to Border Force officers and Norfolk Police were seen in the port area as it was coming in.
A spokesman for industrial manufacturer Siemens Gamesa said the vessel was carrying windfarm towers which were due to be unloaded in Yarmouth for the East Anglia One development and that any delay in their arrival would not be a issue for construction.
The spokesman added: "Siemens Gamesa was notified by its subcontractor that, in the early hours of September 24 while offshore, the crew of the Rotra Mare discovered a number of stowaways.
"The vessel owners have alerted the appropriate authorities."
In 2016 Dutch police stopped a boat with 26 migrants and a map of Sea Palling onboard.
At the time former Metropolitan Police special branch officer Chris Hobbs said the coastline was "extremely vulnerable" with little in the way of defences to stop smugglers.
"You are going to find weak spots given the lack of police and border force officers," he said.
"If you want to move stuff across the North Sea, it is not terrible difficult.
"If you plan what you do well, you have got to be fairly unlucky to be intercepted."
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