Story highlights Two pregnant women were among seven taken to the hospital, ambulance service says

Fifteen children are among 68 people found locked in containers at eastern England port

Four Polish nationals are arrested "on suspicion of facilitating illegal immigration"

London (CNN) UK border agents found 68 people, including 15 children, locked in containers aboard four trucks that had arrived from the Netherlands at a port in Essex, UK authorities said Friday.

The discovery was made when the trucks were searched at Harwich International Port, northeast of London, late Thursday, a UK Home Office spokesman said.

All 68 are now in the hands of the UK Border Force, which is part of the Home Office.

Seven were taken to a nearby hospital with abdominal and chest pains. These weren't considered life-threatening. Two pregnant women were among them, the East of England Ambulance Service told CNN. They've since been discharged from the hospital.

Those found are 35 Afghans, 22 Chinese, 10 Vietnamese and one Russian.

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