Avon and Somerset police have released a 50-year-old man on bail following his arrest in connection with a lorry carrying 15 people near Ilminster.
ITV News understands he is the driver of the lorry.
A force spokesman said: "A 50-year-old man has been released on police bail pending further enquiries. He was arrested yesterday on suspicion of facilitating entry of people into the UK. 15 people who were found in the back of a lorry remain in a rest centre."
More top news
A wet, wintry night in places with rain and hill snow slow to move away from southern Scotland and northern England.
The Westminster terror attack dominates the front pages of Thursday's newspapers.
A timeline of exactly what happened.