Police say they were alerted to the presence of 15 individuals after people reported hearing "noises coming from the back of the lorry".
They previously reported that there had been 20 people onboard.
News: We received several calls earlier this afternoon raising concerns about noises coming from the back of the lorry 1/3
Officers stopped the lorry at a service station on the A303 Southfields Roundabout at Ilminster at about 1pm 2/3
A total of 15 people were found on board including men, women and a 15 year-old boy. Full update to be issued on our website shortly 3/3