Slovak veterinary inspectors found 21 packages of hard-boiled and peeled eggs that were contaminated with fipronil in a warehouse of the western village of Vrbove, agriculture ministry spokeswoman Zuzana Peiger Acjakova told AFP.
Fipronil is commonly used to get rid of fleas, lice and ticks from animals but is banned by the EU from use in the food industry. It can harm people's kidneys, liver and thyroid glands.
The problem is believed to stem from a substance used by Dutch company Chickfriend which farmers in the Netherlands and Belgium say they hired to treat their chickens.
The eggs at the centre of the scandal have mainly come from the Netherlands, followed by Belgium and Germany. Scores of farms have been shut.
Sweden, Switzerland, Britain, France and Luxembourg have also found contaminated eggs, and on Thursday Danish authorities said twenty tonnes of the eggs had been sold there.
Slovak authorities were informed about the shipment of tainted eggs by an EU-wide rapid alert system, Acjakova said.
"Freshness is a criterion that consumers should take into account, because it determines the quality of the product," Slovak Agriculture Minister Gabriela Matecna said in a statement.
"Slovak foodstuffs are under strict control of our veterinary administration from the field to the shelves," she added.
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