More than 4,700 German farms have been closed after large amounts of animal feed were found to be contaminated with dioxin, a poisonous chemical formed by industrial processes and waste burning.

Officials insist the levels of dioxin do not pose a risk to humans, and that the closures are only a precaution.

The origin of the contamination has been traced to a distributor in the northern German state of Schleswig Holstein, where oils intended for use in bio-fuels were accidentally distributed for animal feed.

Initially, the scare was confined to Germany but then it emerged that a batch of eggs had been exported to Holland and from there to Britain.

The dioxin scare has prompted South Korea to block imports of German pork and poultry products from reaching consumers due to health concerns, local media reported on Friday.

European Commission health spokesman Frederic Vincent told a news conference how the problem had now reached Britain.

"Those eggs were then processed and then exported to the United Kingdom... as a 14-tonne consignment of pasteurised product for consumption," he said.

"Whether it went into mayonnaise, pastries, I don't know. So we will probably take a look at this with the UK authorities and see what was done with these eggs."

(Source: Dioxin animal feed scare shuts German farms [BBC])