Seven people have been taken to hospital after dozens of suspected illegal immigrants were found crammed in a container at a port.
The East of England Ambulance Service were called around 10pm about people locked in the container – thought to have come from Holland – at Harwich International Port in Essex.
Two of those taken to hospital were pregnant women.
Four Polish lorry drivers have been arrested on suspicion of facilitating illegal immigration.
Matt Broad from East of England Ambulance Service told Sky News paramedics were on the scene within six minutes of getting a call from UK Border Agency staff.
Two hazardous area response teams, up to six officers and senior ambulance service staff were sent to the incident, he said.
Mr Broad told Sky: “The early indication came back that there was a significant number of people that had been discovered in trailer containers.
“With the numbers being over 60, we launched our full major incident plan and sent resources including our hazardous areas response team so we could ensure that all those people were thoroughly medically checked.”
Of those taken to hospital, Mr Broad said several had fainted, while others were suffering with abdominal and chest pains.
He added: “We do know from experience now that patients that have been in containers or lorries for some period of time can be dehydrated, and suffer other medical effects.”
The Home Office said in a statement: “We can confirm Border Force officers discovered 53 adults and 15 children during a proactive search of four lorries which had arrived at Harwich port from Holland on Thursday evening.
“Seven of those discovered were taken to hospital as a precaution, before being released. All 68 individuals are now in the care of Border Force.
“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 enquiries continue.”
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 following the incident.
A third man, Martin McGlinchey of Coalisland, Co Tyrone, has also been charged with the same offence.
Later that month, one person was taken to hospital after 13 people were found in the back of a lorry at the Dartford Crossing in Kent.