Fifteen people were found alive in the back of a truck on Wednesday after a member of the public reported suspicious activity to the police.
Police stopped the truck on a main road in Wiltshire, 90 miles west of London. They found 15 men in the back, all believed to be between the ages of 16 and 30. All were arrested on suspicion of entering the U.K. illegally, police said.
The driver of the truck, an Irish man in his 50s, was also arrested on suspicion of assisting illegal entry into the country.
The nationality of the 15 individuals is not clear at this stage, police said.
"We were called by a member of the public shortly before 8.30 p.m. this evening following a report of suspicious activity involving a lorry on the A350 near Chippenham," said a police statement on Wednesday evening.
Emergency services attended to the scene and carried out medical checks on the 15 men. One of the men was taken to hospital for further checks but was not believed to be in a serious condition. The others were taken directly into police custody.
"Members of the public would have noticed a large number of emergency services in the vicinity of the A350 last night while we dealt with this incident and the road was closed for approximately four hours while we carried out enquiries at the scene and recovery was arranged for the lorry [truck], which was a hard-sided large goods vehicle,” said Duty Superintendent Steve Cox in a statement.
"I would also like to extend my thanks to the vigilant member of the public who initially reported this incident to us -- it is thanks to them that this incident was resolved swiftly and safely with no serious casualties."
Wiltshire Police have now handed the investigation over to the Home Office as per police procedure.
A further four people have been arrested by police in England connection with the case involving the deaths of the 39 people.
Elsewhere, Eamonn Harrison, 22, of Northern Ireland is currently in Irish police custody in connection with the case. He appeared before the High Court in Dublin at the end of last week and the Crown Prosecution Service has begun extradition proceedings to bring him to face charges in Great Britain.
Two other Northern Irish men, Ronan Hughes, 40, and his brother Christopher Hughes, 34, are wanted on suspicion of manslaughter and human trafficking.
Police believe that the 39 victims are Vietnamese nationals and Essex police are working with Vietnamese officials who were sent over from Vietnam to work with U.K. authorities.