ITV News understands the lorry carrying the 15 passengers belongs to a firm called Thermotraffic and that it stopped in Calais before reaching the UK.
ITV News producer Sandi Sidhu has tweeted:
I'm told that the lorry belongs to Thermotraffic came frm Europe and had stopped in Calais. It was supposed to be carrying general cargo
Police have said the vehicle "originated in mainland Europe" and that it "has been seized as part of our investigation".