THE HAGUE — The European Union on Monday (Aug 7) notified food safety officials 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.

Major supermarket chains in Belgium, including Delhaize and Colruyt, have stopped selling eggs from affected farms. In the Netherlands, one poultry producer declared bankruptcy on Friday as a result of the insecticide scare, according to an industry group.

The Dutch consumer safety authority has published a guide on identifying the tainted eggs through a 10-digit serial number stamped on the shells. The country’s biggest supermarket chain, Albert Heijn, stopped selling many eggs last week, but the company said that eggs were back on sale as normal on Monday. In the Netherlands, an estimated 9 million chickens from about 180 farms have been affected.

In Germany, the supermarket chain Aldi withdrew all eggs from sale after the authorities said that about 3 million eggs imported from the Netherlands had been affected. Since then, fipronil contamination has been found at four farms in the German state of Lower Saxony.

Fipronil is toxic in large quantities and can damage kidneys, liver and lymph glands. The Belgian and Dutch authorities are investigating how the contamination happened.

The Dutch poultry association said that farmers had no idea that cleaners were using the substance. Aalt den Herder, the group’s secretary, said the risk had been overstated.

“It was never an issue of human health, it was an issue of consumer confidence,” he said.

Rik Grashoff, a Dutch lawmaker and the agricultural spokesman for the Green party, said the contamination should “never have happened.” THE NEW YORK TIMES