Czech importers of eggs from the Netherlands and Belgium have been told they must carry out laboratory checks for the insecticide Fipronil. The demand comes from the State Veterinary Administration. After eggs have been cleared they can be sold on the market. Eggs contaminated with the insecticide, which is harmful to humans and should not be used on chickens, have been found in neighbouring Slovakia. Millions of eggs have been withdrawn from the Netherlands, where the contamination took place, and Belgium, where it was first noticed. The insecticide is used against fleas, mites, and ticks.