One person has been taken to hospital after 13 people were found in the back of a lorry amid reports of suspected illegal immigrants.
The discovery was made just after 11am this morning at the Dartford Crossing in Kent, which led to heavy congestion on approaches to the area.
A South East Coast Ambulance Service spokeswoman said the person taken to hospital was not believed to be in a life-threatening condition.
Kent Police confirmed they were called to a report of suspected illegal immigrants but that the immigration service was managing the investigation.
Details of the nationalities and sexes of the people found were not immediately available although no children were believed to have been among them.
The Secamb spokeswoman said: "We attended the Dartford Crossing at 11.38am to reports of a number of individuals who had been found in the back of a lorry.
"We sent two ambulances and our Hazardous Area Response Team (Hart). We were unsure what the situation was.
"Our crews assessed 13 individuals at the scene. One required transportation to hospital and they were taken to the Darent Valley Hospital.
"They didn't appear to be in a life-threatening condition. The other 12 were taken to Dover."
The discovery comes after 35 immigrants were found in a container at Tilbury Docks in Essex earlier this month.
One of them, 40-year-old Meet Singh Kapoor, from Afghanistan, was found dead. The group included 13 children, who are all believed to have fled Afghanistan after suffering persecution.
Two lorry drivers - Stephen McLaughlin, 34, of Limavady, Londonderry, Northern Ireland, and Timothy Murphy, 33 of Elmgrove, Londonderry - have been charged with conspiring to facilitate illegal entry into the UK.
Across the English Channel in Calais, hundreds of migrants, mainly from Africa, are camping or living in squats, which has led to violent clashes erupting on the streets.
Local officials have called on Britain to do more to share the burden of immigration, with the deputy mayor of Calais, Philippe Mignonet, appealing to the historic "Entente Cordiale" between the two nations.
Mr Mignonet said earlier this month that the port town had been saddled with an image of a "theatre of war" as he called on David Cameron to "come and see what we face".
The use of Calais as a stepping stone to Britain has long been a problem for France.
In May, three makeshift migrant camps were evacuated and destroyed amid insanitary conditions and an outbreak of scabies.
In 2002, the French government closed the Sangatte Red Cross centre, near Calais, after repeated lobbying by then home secretary David Blunkett.
This month, it was reported that Calais mayor Natacha Bouchart was planning a state-funded camp away from local residents amid the "unbearable strain" of the high numbers of migrants.