The remarkable thing about the red-brick houses which rise up everywhere among the rocky outcrops and orchards of Fujian province in southern China is that most have no door frames or window glass installed.

Some of the tall, gaunt structures are shrouded in bamboo scaffolding, but most seem abandoned. "No, they're not derelict", a shopkeeper told me just outside in the provincial capital, Fuzhou. "Here, a farmer builds the walls of a house first and then waits for years until a family member abroad gathers enough money to finish it. All these buildings will have people some day."

Those which have been completed, and equipped with typical blue-tinted windows and scalloped tiles, tower over old family shanties as memorials to successful economic emigration, the dream of Fujian people for centuries.

Most of China's illegal migrants, including apparently the 58 found dead in a refrigerated container at Dover on Monday, come from Fujian province. They are not driven by hunger, as there is sufficient food here, but by a fierce desire for a better life for themselves and the families left behind. People know that a job in the United States, Japan or Europe will pay much more than they can get at home.

"I have 60 dollars saved", said a young woman selling jellyfish in the market in Changle, a port city of 680,000 people which is the main departure point for illegal migrants, and which boasts prosperous apartment blocks with balconies protected by metal grilles. "In America, I could get that in one day."

People smiled when I asked if some migrants were fleeing religious or political persecution or the one-child policy, as 119 Fujian residents who reached New York on a container ship in January have claimed. "That's only a story for American immigration", said a woman office worker. "They all go for the money."

Fujian officials make it impossible to fully investigate such claims. On Thursday I was taken into custody by public security officials who arrived in a Pajero and a military-style jeep when I was interviewing a local artist in his studio on a quiet street in the coastal town of Jinfeng.

They pulled my interpreter away and took us to a police station, then to county HQ in Changle, 15 kilometres away, where I found five other correspondents being similarly detained. We were released after being told not to do any more interviews.

Because of the Dover tragedy, the Fujian police are the focus of attention from a Chinese government already under pressure from abroad to curb the activities of the criminal gangs, known as "shetou" or "snakeheads", who smuggle up to 100,000 migrants out of China each year. Hundreds of Fujian officials have already been implicated in a huge oil- and cargo-smuggling racket, and questions are being asked in Beijing about how the snakeheads can continue to operate so freely.

The gangs are suspected of watching the homes of relatives of the Dover victims to make sure they do not make trouble, and they may have tipped off the police about our movements. A Hong Kong journalist was threatened by thugs who tried to seize his equipment after he arrived in the village of Tantou, a notorious snakehead haunt, and located a resident named Liu Yide, who fears that his 25-year-old son, Liu Yifeng, perished trying to reach England.

I found people in Tantou, which I visited before being detained, unwilling to talk. Business is at a standstill because of a seasonal ban on fishing in the South China Sea, which has left the estuary of the Min river clogged with the fishing boats used to take migrants on the first leg of their sea journey.

In Changle, where one in 10 people is said to have gone abroad, a driver told me that people-smuggling is regarded as a more lucrative way of raising capital than cocaine-dealing. "A snakehead will ask 200,000 yuan (IR£20,000) for passage to England and 350,000 yuan (IR£35,000) to America", he said.

"This is more than a worker would make in a lifetime here. A family can make a 10 per cent deposit and pay the rest when they get a telephone call to say everything went OK, or they can pay by instalments with money sent home."

A youth with his hair dyed orange who sold dry goods in the market said: "I will leave as soon as I can, as many of my friends are already in America, but I will do it legally, because it's getting too dangerous now."

He was referring to a current crackdown on snakeheads and their customers, rather than the physical risks involved. Police in Fujian province detained 171 snakeheads from January to March, and last year seized 2,173 illegal emigrants, who face two-year jail terms. From January to September last year, 29 groups totaling 3,060 migrants were returned by foreign countries.

The anti-snakehead campaign was underlined by big red characters painted on walls saying "Resolutely combat evil people smuggling".

"It's much more difficult to get out now", said a motorcyclist in a conical bamboo helmet. "Years ago, almost anyone who wanted could leave. Now most are caught."

The full horror of what happened in Dover has had little apparent impact in Changle. In the busy market many people said they had not heard the news, though it has been published in Chinese newspapers. "I didn't know, I just get on with my business", a shell-fish seller said.

There is a conspiracy of silence about the dire conditions migrants endure, said a long-time observer of Fujian migration. People stay quiet because of the danger of reprisals by snakeheads against informers and their families, despite the documented cases of Chinese migrants found chained in ships without food or water, taped from head to toe and left in closets to die. In January, three Chinese were found dead in the hold of a container ship in Seattle with 15 other men and youths.

There is also some antipathy from those with no relatives abroad towards returned emigrants. "They make big money, then they come and put up big houses like emperors and go away again", said a pensioner in Jinfeng, which has a "widows' village" from which all the men have gone to the United States. A woman tending vegetables beside a foetid pond said: "They all think the United States and England are very beautiful, so they want to live there."

Many Fujian residents perhaps prefer not to know what might be in store, aware that they will become migrants as part of a historical tradition which has created an overseas Chinese community of 55 million, of whom 90 per cent are from Fujian and Guangzhou provinces.

They mostly want to go to Japan or the United States, but because it is harder and more expensive to get there today, western Europe has become more attractive. The journey to Europe usually starts at Fuzhou railway station, from where they go in groups of 60-80 to Beijing.

Snakeheads give them food for the journey and arrange for agents to meet them at various points. They travel on by rail to Moscow and then to the borders of the Czech Republic and Hungary.

For many, the odyssey ends in a restaurant kitchen or a brothel, where they are held as virtual slaves until the snakeheads are paid off. The lucky ones eventually get good jobs and send enough money to their families to pay off the gangsters and finish the red-brick house that their parents started. There framed photographs of their smiling, prosperous countenances are hung on the wall to encourage a new generation of Fujian people to take their chances on the other side of the world.