The Home Office said tonight that 13 people found in a lorry in Kent, whose nationalities have yet to be confirmed, will be questioned later.
Officials had this warning for lorry drivers entering the UK:
Drivers and hauliers must take adequate steps to secure their vehicles from illegal immigrants trying to smuggle themselves across the border.
If a driver does not take these steps - and is found with people hiding in their vehicle - they will be issued with a civil penalty.
More top news
Downpours keeping us on our toes today
The M20 in Kent has been closed in both directions after a pedestrian bridge allegedly collapsed on the motorway on Saturday.
The AA have warned of traffic jams and urged people to carry extra water in their vehicles because of the warm weather.