Update: The Irish man arrested by police in England on suspicion of assisting 15 people with illegal entry into the UK has been released from custody.
The people were found in back of Cork-owned lorry being driven by the man in his 50s last night.
The 15 men are aged between 16 and 30 and 14 of them were taken into custody, while the fifteenth was brought to hospital before being arrested.
The driver's firm, Sean Delaney International Transport, said he is now free to return home.
Fifteen people have been found in the back of an Irish-owned lorry in south-west England following reports of “suspicious activity” involving the vehicle.
Police in Wiltshire arrested an Irish man in his 50s on suspicion of assisting with illegal entry. He is in custody in Swindon.
All of the people who were discovered in the lorry, owned by Glanmire's Sean Delaney & Sons, in Chippenham are believed to be over the age of 16 and none is thought to be in a serious condition, according to police.
The fifteen people have been arrested on suspicion of immigration offences.
One man was taken to hospital as a precaution but was later released into custody.
The other 14 people were deemed medically fit and were taken straight into custody on suspicion of immigration offences.
Wiltshire Police said the force was "not clear" about the nationalities of the 15 at this stage.
A police spokesman said: “We were called by a member of the public shortly before 8.30pm this evening following a report of suspicious activity involving a lorry on the A350 near Chippenham.
“Officers attended the scene and located 15 people in the rear of the vehicle.
Sean Delaney & Sons confirmed that their vehicle was involved in the incident.
"We can confirm that the truck involved in last nights incident in Chippenham was one of our ‘Delaney Transport Trucks," the company said in a statement to The Neil Prendeville Show on Cork's RedFM.
"Our driver was on the way from Callais to Dover. The driver heard knocking and thought it was a flat tyre," Mr Delaney said.
As the knocking continued "the Delaney transport driver then immediately called the Police who arrived to find 15 people in the back of the trailer."
"The driver was taken to the nearest police station and has been questioned. Mike Delaney has been co-operating with the police all morning and will continue to do so. His driver is also co-operating with Police."
It comes after eight people were arrested earlier this week by Vietnamese police in connection with the 39 migrants found dead in a lorry in Essex.
- Additional reporting Liz Dunphy and Press Association