LONDON (AFP) - The frail survivors found inside a shipping container at a British port at the weekend following a "horrific ordeal" are Sikhs from Afghanistan, police said Sunday.

One man was found dead in the container, and 34 men, women and children - all suffering from severe dehydration and hypothermia - were found still alive Saturday after staff at Tilbury Docks, east of London, heard banging and screaming coming from inside.

All the survivors were taken to nearby hospitals, where four remain, and the local Sikh community has been helping with their religious and clothing needs.

Using interpreters, police intend to interview the survivors to pin down how they came to be found in such circumstances.

The container had arrived by truck at Zeebrugge seaport in Belgium around 12 hours before the people inside were discovered at Tilbury, having crossed the North Sea on a ferry.

They may have been inside the container for several hours before that.

"The welfare and health of the people is our priority at this stage," said superintendent Trevor Roe, of the local Essex police.

"Now they are well enough, our officers and colleagues from the Border Force will be speaking to them via interpreters so we can piece together what happened and how they came to be in the container.

"We now understand that they are from Afghanistan and are of the Sikh faith.

"We have had a good deal of help from partners within the local Sikh community in the Tilbury area to ensure that these poor people, who would have been through a horrific ordeal, are supported in terms of their religious and clothing needs."

Thirty of them have been released from hospital, and the remaining four were likely to be discharged later Sunday.

The Red Cross provided food and welfare for them overnight Saturday.

The Border Force will take care of them once officials have finished questioning them.

Because a body was found, police have launched a homicide investigation, though none of the survivors is under suspicion. A post-mortem into the man's death was being conducted Sunday while forensics experts were examining the container.

Tilbury port has resumed business as usual.

Cases of immigrants trying to enter Britain illegally, often in dangerous circumstances, are not rare.

The BBC quoted the UK Border Force as saying that in the year 2012-13, more than 11,000 attempts to cross the English Channel from continental Europe illegally were prevented at "juxtaposed controls".

In June, eight suspected illegal immigrants, all Afghan nationals, were rescued from the English Channel when their small boat lost power.

Tony Smith, a former head of the UK Border Force, said people being trafficked into Britain were the victims of criminal gangs.

"They're being exploited because the prize is a passage to the West," he told the BBC.

"They want to migrate to the UK or to Europe but they're being exploited by criminal gangs who are probably taking their entire life savings away.

"We really need to get a message out to migrants that if they want to come to this country there are legal routes that they need to explore and they need to apply for visas and permits."