The unidentified manager was arrested after the cancer-causing chemical, dioxin, was found in fat products from his company, Fogra, in southern Belgium.

Fogra was supplying the fats to an animal feed company called Verkest, which was originally suspected of being responsible for dioxin entering the food chain. The owners of Verkest have now been released from custody.

The owner of the Verkest factory has been released

Investigators suspect that, inadvertently or otherwise, motor oil was mixed in with a consignment of fat intended to be turned into animal feed.

The arrest came on the day after the European Commission started legal proceedings against Belgium over its delay in confronting the crisis.

Belgium 'broke rules'

A Commission spokesman said that, by waiting so long before sounding the alarm, Belgium had failed to follow European Union rules on consumer protection and information.

Belgian authorities began investigating when chickens started dying back in January.

By late April dioxin poisoning was confirmed. It was traced back to fats mixed in animal feed but it was not until the end of last month that the EC was informed.

A ban on chicken, eggs, as well as pork and beef, followed, but hundreds of farms had already received the contaminated feed - some of them in the Netherlands and France.

While products from unaffected farms are back on supermarket shelves in Belgium itself, farmers and the food industry are still suffering the effects of worldwide restrictions on the country's produce.

Farmers protest

On Monday, about 6,000 farmers demonstrated in Brussels to protest at the government's handling of the crisis and to demand compensation.

Coca-Cola was withdrawn from sale

Belgium has also been hit hard by the latest European food scare, in which Coca-Cola bottles and cans are being withdrawn from its shelves and those of Luxembourg, Holland and France.

More than 100 Belgian children fell ill after drinking Coca-Cola containing the wrong carbon dioxide gas.

Now the company is trying to restore its good image, taking out a full-page advertisement in Belgian newspapers to apologise for any discomfort or ailment caused by its products.