Now, four months later, the poisoning of millions of chickens, pigs and cattle has brought Belgian agriculture to a standstill, cleared the supermarket shelves of food, and forced the internationally renowned luxury chocolatier Leonidas to close its shops. It has led to the resignation of Belgium's agriculture minister, and the sense of betrayal felt throughout the country could bring down the government at this weekend's national and European Parliament polls.

From Hong Kong to the United States, Belgian and other European Union products are banned. The EU itself has ordered suspect Belgian products off the market.

But in March no-one was thinking of international scandals.

It all began at that one farm, but the way in which cancer-causing dioxin may have got into animal feed, how it spread and how the feed industry has reacted is a damning story of how modern food is produced.

Dioxin is produced during burning of plastics and other industrial processes, and may be present in many chemical wastes from used car oil to transformer coolants. That one of these wastes may have become mixed with recycled animal fat from Belgium's street chip stalls, which then went into animal feed, is just one remarkable facet of a remarkable story.

At De Brabander's farm in March, no-one wanted to worry hypersensitive consumers or undermine confidence in Belgium's lucrative agri-business. The death of the chickens was still a veterinary problem, a private matter between a farmer and his wallet.

Clearly, however, the insurance company had to find out fast what was going on.

The insurer sent in a veterinary expert, Andre Destikkere. It took two weeks of thorough investigation for the inspector to decide that fat mixed into the feed in January was at the root of the problem. Dr Destikkere had samples of fat and chicken meat sent off to Holland for testing. De Brabander informed the ministry of agriculture.

In the race to provide the cheapest feed for Belgium's vast poultry and pork industries, cutting corners on quality is part of the game. Feeders are supposed to use fresh animal fat. In fact, it appears that recycled animal fat collected from Belgium's ubiquitous chips-with-mayonnaise stalls may have been used without proper labelling.

But while recycled cooking fat may be unpleasant, and should be labelled, it does not generally contain dioxin.

The problem seems to be that the fat was collected from specially provided recycling vats at public waste depots. Someone may have poured another, more noxious substance into the vat - possibly transformer coolant - probably to save the 1,000 euro (HK$8,130) per-tonne cost of removing cancer-causing pollutants such as polychlorobiphenyls and dioxins by more conventional methods.

The inspector sent the samples to Holland on March 18. Apparently he must have suspected dioxin poisoning even at that early stage. Not only did he choose a Dutch laboratory, knowing Belgian facilities were ill-equipped to trace the chemical, but his hunch seemed to have spurred the authorities into hunting for contamination long before the official test results came back on April 24.

According to the Belgian Government's own belated report, Verkest, the company which supplied the fat, was investigated on March 24, after De Brabander gave the ministry a list of its suppliers. That was two months before the EU Commission was informed. The firm's suspicious labelling and administrative practices were reported to the public prosecutor's office. Three samples were taken from its tanks of fat.

After analysis, said the report, the samples 'appear not to contain dioxin'. In other words, they were tested for dioxin, but since the results did not come back until May, there was no evidence either way.

Only when the tests on the fat supplied to the poultry breeder showed heavy dioxin contamination did the ministry go back to Verkest and impound its tanks, start tracing the fat it sold to feed mixers in Belgium, France and the Netherlands and begin testing the feed mixed by its clients.

A month later it went public and banned the sale of poultry and eggs. But by that time, chicken, eggs, dairy products and pork contaminated with dioxin had all made their way into the market and on to the family menu. Agriculture minister Luc Van den Bossche, who took on the job when his predecessor was forced to resign, accuses his EU partners of protectionism and of opportunism.

He has argued against the banning of Belgian fresh milk, saying any contamination would be well below the international safety limit. And on Friday the Belgian Government authorised sale of meat and dairy products from farms not proved to have used contaminated feed, against EU demands that the country wait until full tests had been carried out.

Mr Van den Bossche's farmers are having to watch their livelihoods destroyed along with their contaminated livestock, as truckloads of food from their European competitors stream in to plug the yawning gap in the food market.

Mr Van den Bossche claims a similar mistake could have happened anywhere. Controls over what goes into animal feed, he says, are inadequate all over Europe. Consumers 'may have eaten a lot in Europe, without knowing what we are eating'.

Meanwhile, he briefly lifted the ban on slaughter and export of produce from the roughly 75 per cent of the country's 3,200 chicken farms the government believed had not bought contaminated feed. Then he had to bring the ban in again, when one major feed compounder admitted it had bought ingredients from Verkest, even though it was not on the official blacklist.

Suddenly, half of Belgium's chicken farms were suspect. The number using potentially dodgy feed had doubled overnight.

So far, despite the minister's efforts, the government's policy of 'restoring consumer confidence, whatever the cost', does not seem to be cutting much ice.

A highly topical report by Ghent University criminologist Brice De Ruyver, commissioned by the justice ministry before the dioxin scare broke, recently came up with a long list of allegations of corrupt links between policemen, veterinary inspectors, the farming industry and criminals supplying illegal hormones.

So this weekend, disillusioned voters, sick of their shady, corruption-prone politicians, were expected to swing in droves to the environmentalists - or, at the other end of the political spectrum, to the extreme right.

The public feels betrayed, uncertain and unsure whom to trust. Not only do they have conflicting assessments from their own government and the European Commission on what foods are safe to eat, but even the medical reports on dioxin are contradictory.

On the one hand, dioxin is always mentioned as a cause of cancer, is known to accumulate permanently in body fat and therefore to have no safe maximum dose. Mothers of both human and other animal variety can pass it on in their milk - hence the worry over Belgian dairy products. It is thought also to reduce sperm count in men.

It was present in batches of Agent Orange, the defoliant herbicide used by US forces to destroy enemy cover in the Vietnam War.

It was found in the Love Canal dumping ground in New York State in the 1970s, forcing residential areas to be evacuated.

And thousands of residents in Seveso in Italy were showered in dioxin after a chemical plant exploded in 1976. There, some 450 victims developed the disfiguring skin disease chloracne, as a direct result of the disaster.

Yet, the World Health Organisation (WHO) sets a 'tolerable daily intake' in recognition of the fact that dioxin is a by-product of modern industrial processes. It is present in the air, soil and in food - although background levels have been falling since governments began to clamp down on industrial emissions of the substance.

Strangely, too, in the 23 years since Seveso, the US National Institute of Environmental Science says there has been no unusual incidence of disease in the victims apart from the chloracne.

The Belgian health ministry suggested it might convene an international expert panel to set a daily dose which might be acceptable on a short-term basis.

That might be seen as a cynical move to allow the government to release contaminated food onto the market, but anyone eating the contaminated chicken already sold would already have been exposed to many times the WHO daily intake of one to four picograms - one picogram is 0.000001 micrograms - per kilogram of body weight.

Meanwhile, Jan and Julian Verkest, the father and son team who own the suspect fat renderer, are under arrest. They are in trouble, not for allegedly poisoning their compatriots, a crime which they may have committed unwittingly, but for fraudulently using recycled cooking fats from chip stalls without proper labelling, instead of fresh animal fats. The charitable view is that the Verkests did not know what they were getting with the fat.

The French government has now called for an EU-wide ban on the use of animal meal in feeds, in response to the public outcry and to the devastating experience of mad cow disease or bovine spongiform encephalopathy. BSE was passed on to humans after they ate beef from animals infected by diseased offals mixed in their feed.

The French and Germans are now Europe's biggest producers and consumers of animal meal, which is ground from slaughterhouse wastes, dead animals and even road-kill.

The fact they are even prepared to propose a ban - and the fact that post-BSE Britain is now one of Europe's smallest users of animal meal - shows that animal fats have never been necessary in feeds for naturally vegetarian farm animals.

It was always a matter of convenience and cost.