Emergency officials say a dead man and 35 survivors, including women and children, have been found inside a shipping container being unloaded in eastern England.
They were found inside the container at Tilbury Docks in Essex, east of London on Saturday.
Workers at Tilbury, the main port for the capital, made the discovery on board a P&O cargo vessel that had arrived from Zeebrugge port in Belgium. Officials reported hearing banging sounds.
The East of England Ambulance Service said it sent seven ambulances and other emergency teams to treat the immigrants for hypothermia and dehydration. The 35 survivors were transferred to three hospitals.
Because a body was found, Essex Police have launched a homicide investigation.
Of 64 containers aboard the P&O ship that arrived early on Saturday, police have opened 30 so far to check for any other people.
'Screaming and banging'
"Staff here at the port became aware of screaming and banging coming from a container," police superintendent Trevor Roe told reporters.
"As a result of that noise, staff were alerted and immediately breached the container to find 35 persons within that unit.
"We believe them to come from the Indian subcontinent."
Roe revealed that the survivors were recovering "fairly quickly in most cases" at nearby hospitals.
P&O Ferries said the container arrived on the quay in Zeebrugge around an hour before it was loaded onto the ferry.
Two hours later, the ship began the eight-hour overnight crossing. The people were discovered on the ship's arrival in Tilbury.
Roe said the police investigation would look into "the gangs or whoever may be involved in this conspiracy to bring these people in this way over to this country.
"Clearly we need to try to bring them to justice."
Tilbury, on the River Thames, is primarily a bulk cargo and container port and not such a prime target for immigrants as those on the south coast, such as Dover.
In 2000, 58 Chinese immigrants suffocated to death after the air vent to their sealed container on a truck was closed on their way to Dover.
In July last year, British police arrested two people after 15 asylum seekers were found hidden in a tanker on board a ferry at Dover.
And in June, eight immigrants, all Afghan nationals, were rescued from the English Channel when their small boat lost power.