Denmark has traced 20 tons of imported eggs tainted with the insecticide fipronil, the Scandinavian country's national food safety authority said Thursday.

A Danish firm imported the peeled, boiled eggs from a Belgian supplier. The eggs were produced in the Netherlands, the Danish Veterinary and Food Administration (DVFA) said.

"The eggs were mainly sold to professional kitchens [in Denmark] but not to ordinary consumers," Nikolas Kühn Hove, head of the alert unit for food and feed, told dpa.

The shipment covered August. Typically each basket of eggs contained 4 kilos.

Tests conducted in the Netherlands suggested that although the eggs were tainted with fipronil, the levels were not considered a health hazard. However, they were still illegal to sell in the European Union, he added.

Denmark is among a growing number of European countries affected by the contamination scandal.