THE HAGUE — The European Union on Monday notified the food safety authorities in Britain, France, Sweden and Switzerland to be on the lookout for contamination in eggs after a food scare in Belgium, Germany and the Netherlands.

Anna-Kaisa Itkonen, a European Commission spokeswoman, said, “We do not know if the eggs are contaminated or not, but because of these notifications, it’s now up to the national authorities to check.”

The scare over contaminated eggs, which began in Belgium, has led supermarkets there and in Germany and the Netherlands to clear shelves of the product as the crisis entered its third week.

The removal of eggs from shops was prompted by the discovery of the insecticide fipronil in some shipments. The contamination is thought to have been caused by the mixing of the insecticide with a cleaning agent used at chicken farms. The scare began July 19 when the government of Belgium said that fipronil had been found in eggs produced there.