Four stowaways found on a cargo ship in the Thames Estuary have been detained after the vessel's crew was threatened.
The Grande Tema's crew had to lock themselves in the vessel's bridge for safety, a spokesman said.
Essex Police said the vessel was boarded and secured shortly after 23:00 GMT on Friday - almost 14 hours after the force was first called.
Four men who were on the ship have been held under the Immigration Act, the force added.
The stowaways had demanded to be taken to the coast, according to the ship's owner.
Police previously said the situation was not being treated as a hostage, piracy or terror-related issue.
GPS trackers showed the 71,000-tonne ship sailing in circles in the Thames Estuary. It had set off from Lagos, Nigeria, on 10 December. It docked at Tilbury just before 04.30 GMT.
Grimaldi Group, which owns the vessel, said the four stowaways were discovered on board four days ago.
They were put under surveillance in a cabin but escaped earlier and made threats to the ship's master as the vessel approached Tilbury, urging him to get close to the coast.
Grimaldi spokesman Paul Kyprianou said: "The vessel was coming from Nigeria and was bound to Tilbury and those four stowaways were in the cabin.
"Today they managed to escape from the cabin and they started threatening the crew, requesting the master of the vessel [navigate] very close to the coast.
"That request was probably because they wanted to jump and reach the British coast."
He said the crew had locked themselves in the command area of the vessel.
Mr Kyprianou added: "It's a small group but obviously you can understand it would be scary."