The scandal has affected sales of chicken, eggs, pork, beef and dairy products and caused countries around the world to close their borders to Belgian products and some, including the United States, to impose temporary bans on all EU countries.

EU veterinary experts on Monday backed current measures to combat the debacle as the number of Belgian farms that may have received animal feed tainted with the toxic chemical climbed to 1,400.

The commission's decision requiring Belgian exporters to certify their products dioxin-free and the authorities' failure to draw up full documentation on where the suspect feed had gone meant trade was effectively on hold, EU officials said.

The dioxin is believed to have spread to animal feed from a Belgian fats and oils processing company, but exactly how the chemical entered the productionchain remains unclear.

EU officials have said some 98 tonnes of fat may have been contaminated and this had been used to produce 1,060 tonnes of tainted animal feed.

Some tainted feed has been used on French and Dutch farms.

EU officials are also due to speak to the French government on Tuesday to review measures taken there and decide if further action is needed.

The Dutch agriculture ministry said late on Monday it had lifted restrictions on all but two farms in the country after tests had shown only normal levels of dioxin.

Belgium banned butter sales on Monday because it is a high-fat food, making it particularly susceptible to retaining dioxin, which remains lodged in the body for years.

Belgian media have constantly revised upwards estimates of how much the crisis could cost the country. The latest price tag is some 30 billion Belgian francs ($767 million).

Over the past 10 days, the scare has spiralled into a major crisis, virtually paralysing Belgium's meat industry and rocking thegovernment in the run-up to Sunday's general election.

The European Commission has been outraged by Belgium's delay in notifying it of the poisoning -- the authorities first became aware of dioxin contamination in late April. Legal action against Belgium has not been ruled out.