The discovery of 68 suspected illegal immigrants locked in four lorries of Polish washing machines is one of the "biggest single finds of clandestines coming into the UK", an MP has said.
They were discovered during a routine search at Harwich International Port in Essex at about 10pm yesterday.
Among the 35 Afghan nationals, 22 Chinese nationals, 10 Vietnamese and one Russian passenger, were 15 children and two pregnant women.
Four Polish lorry drivers have been arrested on suspicion of facilitating illegal immigration.
Speaking at the port, Bernard Jenkin, MP for Harwich and North Essex, said it was "one of the biggest single finds of clandestines coming into the UK in this fashion".
He added that the people were discovered in trucks "full of Polish washing machines".
Mr Jenkin said the 68 individuals will probably be told to "go home" but that it is likely "every single one of them" will claim asylum, which could lengthen the process.
He said that 94% of the trucks go through unchecked, so it was therefore possible more migrants got through this way than is known.
After being found, seven of the immigrants - including the two pregnant women - were taken to Colchester General Hospital to be checked, before being released into the care of Border Force officials.
A Home Office spokesman confirmed that 53 adults and 15 children had been found during a "proactive search".
He continued: "Four Polish nationals, who were driving the vehicles, have been arrested on suspicion of facilitating illegal immigration.
"They have been taken to separate police stations and will now be questioned by the Home Office's criminal investigations team while inquiries continue."
All 68 individuals are now in the custody of the Border Force.
A spokeswoman for Stena Line said the Stena Hollandica ferry left the Hook of Holland at 2.15pm and arrived in Harwich at 7.45pm yesterday - a five-and-a-half hour journey
Staff and volunteers from the British Red Cross were soon at the scene responding to any immediate needs.
The charity confirmed that all of the non-European migrants were found locked in four separate vehicles and that it was providing practical and emotional support, including blankets, food and hygiene packs to those affected.
Following a search at Harwich last February, two illegal immigrants plunged to their deaths after jumping from a ship in an attempt to swim to shore.
Artur Doda, 24, and Leonard Isufaj, 27, both from Tirana, Albania, were seen leaping from one of the world's largest ferries, the Stena Britannica, about 1,600ft off Harwich at about 9.50am on February 26.
They were found in the back of a lorry along with 13 others of mixed nationalities after it was randomly selected for X-ray as it entered the port six hours earlier.
An inquest at Chelmsford heard that Mr Doda was sliced to death by the "machete-like" motion of the ship's propeller and Mr Isufaj drowned after they were both sucked underwater almost immediately after jumping over the side, 10 minutes into the journey back to the Hook of Holland.
Coroner Eleanor McGann recorded that both men died accidental deaths.