EDE, NETHERLANDS (AFP) - In the dark and silent shed of a small Dutch poultry farm, 1.8 million eggs closely packed together wait to be destroyed.

In the barn, the machine that sorts and packages the eggs has been shut off and its rolling belt is starting to gather dust. In the empty courtyard, the woman of the house and a worker perform small jobs.

But the fields are empty and the chickens are invisible.

Wim Ten Ham's farm in the central Dutch town of Ede - where dozens of poultry farms are reputed for their eggs - is one of hundreds of farms whose eggs are suspected of having been contaminated by the insecticide fipronil.

Contamination with the toxic chemical has prompted supermarkets in Belgium, the Netherlands and Germany to remove millions of eggs from their shelves, including the discount supermarket giant Aldi which announced on Friday it was pulling all Dutch eggs from stores in Germany.

Authorities in Switzerland and Sweden also said they were tracking shipments and removing eggs, as the impact of the affair widened.

The Dutch food authority (NVWA) also shuttered 138 poultry farms - about a fifth of those in the country - and warned that eggs from another 59 farms contained high enough levels of fipronil that it warned they should not be eaten by children.

Fipronil is commonly used in veterinary products to get rid of fleas, lice and ticks. But it is banned from being used to treat animals destined for human consumption, such as chickens.

In large quantities, the insecticide is considered to be "moderately hazardous" according to the World Health Organisation, and can have dangerous effects on people's kidneys, liver and thyroid glands.

"We are closed and will remain closed until we are able to prove that fipronil has been eliminated from our chickens and is no longer present in our eggs," Ten Ham said.

When his farm's eggs were tested, authorities found that they contained 0.30 mg/kg of the toxic insecticide when only a level of 0.005 mg/kg is allowed.

To eradicate fipronil from his farm, Ten Ham has two choices: destroy all 68,000 of his chickens, which would cost 400,000 euros (S$640,937), or induce a moult and evacuate the birds' droppings.

According to members of the Dutch poultry union, fipronil is lodged in the chickens' abdominal fat and moulting can reduce it, as the agriculture site Boerderij reported.

During moulting, which generally begins in autumn due to the decrease in light, the bird sheds feathers and loses fat.

Ten Ham has since plunged his nearly 70,000 chickens into darkness and put them on a modified diet to make it easier for them to lose fat.

Chickens can remain contaminated for between six and eight weeks.

"I feel powerless," Ten Ham said, adding that he understood rules needed to be upheld, but lamented the strict regulations.

"It's trade protectionism," he said. "It's only to keep the economy going".

Belgian officials admitted on Saturday they knew in early June there was a potential problem over eggs contaminated with fipronil, but kept it secret because of an ongoing fraud investigation.

German Agriculture Minister Christian Schmidt has pressed the authorities, particularly in Belgium and The Netherlands, to clear up the situation, which he said was done with "criminal intent".

It is believed the toxic substance was introduced to poultry farms by a Dutch business named Chickfriend, which was brought in to treat red lice, a nasty parasite in chickens.

Dutch and Belgian media reports that the substance containing the insecticide was supplied to Chickfriend by a Belgian firm have not been confirmed.

Belgium's food safety agency (AFSCA) has said a criminal probe, in cooperation with prosecutors, had been launched.

With losses expected to run into millions of euros, it is another blow for Dutch poultry farmers after 190,000 ducks were culled in November amid a highly infectious strain of bird flu.

Ten Ham has no choice but to wait until fipronil disappears and his eggs are back to containing acceptable levels of the insecticide before he can count up his losses.

"Those who decide pay: they determine the rules, they decide that these eggs are not good enough," the farmer said. "We have to at least talk about compensation. Or else the entire sector is doomed."

Dutch authorities said on Friday that emergency aid had been released to help farmers affected by the scandal, according to the Dutch press agency ANP.

Even if he has to destroy millions of eggs he feels are safe for consumption, Ten Ham is hopeful that talks with the authorities will yield "a clarification so farmers can keep their chickens".

According to Dutch media, about 10 billion eggs were produced in the country last year by about 1,000 poultry farms, with many of them going across the border into Germany.