Four Polish lorry drivers have been arrested on suspicion of immigration offences after Border Force officers found 53 adults and 15 children during a search of lorries which had arrived at Harwich port from Holland, the Home Office said.
Two pregnant women were taken to hospital after at the port with dozens of other suspected illegal immigrants.
Seven people were taken to Colchester General Hospital and 61 others assessed by the East of England Ambulance Service, which was called about the container at Harwich International Port at around 10pm on Thursday.
An ambulance spokesman said: “The patients who were taken to hospital were suffering from abdominal and chest pains and were feeling faint.
“None are in a life-threatening or serious condition.
“The remaining 61 were released to the UK Border Agency officials.”
The spokesman said a range of different nationalities was involved, both men and women, including two who were pregnant, and who were among those taken to hospital.
The Home Office said that, contrary to earlier information provided by the emergency services about the incident, the passengers had not been found in a container, but had travelled to the UK in lorries on the ferry.
In August last year 35 immigrants were discovered in a container at Tilbury Docks in Essex.
One of them, 40-year-old Meet Singh Kapoor, from Afghanistan, was found dead.
The group, whose ages ranged from one to 72, are believed to have fled Afghanistan after suffering persecution.
Two lorry drivers, Stephen McLaughlin, of Limavady, Londonderry, Northern Ireland, and Timothy Murphy, of Elmgrove, Londonderry, have been charged with conspiring to facilitate illegal entry into the UK.
A third man, Martin McGlinchey of Coalisland, Co Tyrone, has also been charged with the same offence.
Later the same month, one person was taken to hospital after 13 people were found in the back of a lorry at the Dartford Crossing in Kent.
Essex Police said in a statement: “The ambulance service contacted police at 10.15pm on Thursday June 4 to reports they had been called to deal with 68 patients who had been discovered in containers on a ferry from the Hook of Holland at Harwich Port.
“Essex Police made contact with staff at Border Force, who were already in attendance, and they are taking the lead as the incident relates to immigration offences.
“We are continuing to liaise with Border Force while their inquiries continue.”
Following a search at the same port in February last year, 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 500 metres (1,600ft) off Harwich at about 9.50am on February 26 2014.
They had been 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.
It is thought they were part of a group which had broken into the vehicle without the driver’s knowledge as part of an organised people smuggling operation.
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, ten minutes into the journey back to the Hook of Holland.
Mr Isufaj’s body was found on March 20 on Felixstowe beach while Mr Doda was found floating in the water off Essex on April 29.
Coroner Eleanor McGann recorded a conclusion that both men died accidental deaths, adding that it was difficult to make recommendations to the Government based on this case.
“This is all part of a bigger picture on immigration and how it’s handled, and nothing I could say could help prevent such sad deaths in future,” she said.
A spokesman for the port said the stowaways were discovered on vehicles that had arrived on the Stena Hollandica.
A spokeswoman for Stena Line said: “We can confirm that four different lorries carrying 68 clandestines were stopped by Border Force at Harwich International Port last night as they disembarked from the Stena Hollandica.”
She added that the ship left the Hook of Holland at 2.15pm and arrived in Harwich at 7.45pm yesterday – a five- and-a-half-hour journey.