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The Dutch food watchdog has said allegations it knew about a potentially dangerous egg contamination as early as last year are "untrue".

But NVWA inspector-general Rob van Lint did admit to receiving an anonymous tip-off that a harmful insecticide had been used in November.

The chemical in question, fipronil, can harm people's kidneys, liver and thyroid glands.

It is used to treat lice and ticks in animals, and as a general insecticide.

It is not approved for use in the food industry.

In this case, it had been used to clean chicken pens in order to combat red lice, the NVWA said in a statement.

But Mr van Lint added: "At that time there was no indication of an acute danger to food safety. There was not a single indication that fipronil could also be present in eggs."

The problem first came to public attention in August, when Aldi pulled all its eggs from sale in Germany.

It has since emerged Belgian officials knew about the contamination in June, but did not make the information public.

But Belgian Agriculture Minister Denis Ducarme turned the blame on the Netherlands during a hearing on the crisis in the Belgian parliament, saying the neighbouring country knew about fipronil in eggs as far back as November.

However, Dutch authorities had made "no official communication", he said.

Belgian and Dutch authorities are categorising the destruction and recall of eggs as a precautionary measure.

The Netherlands is Europe's biggest egg producer - and one of the largest exporters of eggs and egg products in the world.

It exports an estimated 65% of the 10 billion eggs it produces every year.

More than 100 poultry farms have been closed during the investigation.

When Belgium initially came under fire for not reporting its detection of the chemical in early June, a spokesperson said they had delayed reporting the contamination because the case had been referred to a prosecutor over a fraud investigation.

The cause of the contamination is not yet clear, but a number of reports have suggested fipronil may have been mixed with another insecticide to improve its effectiveness.