Four supermarkets have taken products off their shelves in the wake of the egg contamination scare – as the Food Standards Agency says the scale of the problem is higher than previously thought.

Around 700,000 eggs from Dutch farms implicated in the Fipronil contamination scare have been distributed to Britain, rather than the 21,000 first estimated, the watchdog said.

In response, Sainsbury’s, Morrisons, Waitrose and Asda have withdrawn a total of 11 products – including sandwiches, sandwich fillers and salads – from sale.

The FSA said investigations into the incident suggested it was “very unlikely” that the eggs posed a risk to public health as it released a list of processed products withdrawn in the UK “to ensure that consumers are protected”.

The move came as Dutch investigators detained two men suspected of being involved in the illegal use of the pesticide at poultry farms.

Potentially contaminated eggs have cropped up in Luxembourg, Denmark and Romania, with the Veterinary Health Authority in Bucharest saying it discovered 1,000 kilograms of eggs before they reached supermarket shelves.

Morrisons (Jon Super/PA)Morrisons is among the four supermarkets which have withdrawn egg products from sale (Jon Super/PA)

The FSA said all products withdrawn in the UK were processed foods in which egg was one ingredient among many others, mostly used in sandwich fillings or other chilled foods.

It said some of the products made from these eggs would have already been consumed, but some were still within the expiry date and were being withdrawn by the businesses involved.

Many of the eggs were mixed with others which had not come from affected farms so Fipronil residues would be highly diluted, it added.

FSA chairwoman Heather Hancock said: “I’m confident that acting quickly is the right thing to do.

Eggs (Guido Kirchner/AP/PAThe FSA said it was “very unlikely” that the eggs posed a risk to public health (Guido Kirchner/AP/PA)

“The number of eggs involved is small in proportion to the number of eggs we eat, and it is very unlikely that there is a risk to public health.

“Based on the available evidence there is no need for people to change the way they consume or cook eggs. However, Fipronil is not legally allowed for use near food-producing animals and it shouldn’t be there.”

The FSA said it had no evidence that eggs laid in the UK were contaminated or that Fipronil had been used inappropriately here, and testing results to date for England and Wales showed no exposure to the pesticide.

Eggs (Marcel Kusch/AP/PA)The FSA said it had no evidence that eggs laid in the UK were contaminated (Marcel Kusch/AP/PA)

Meanwhile, EU officials said 15 European Union members plus China and Switzerland have reported receiving contaminated eggs or egg products.

Several producers in the Netherlands and Belgium are under investigation, and EU trade and agriculture spokesman Daniel Rosario said farms have also been blocked in France and Germany.

He named 13 other countries that have received products from affected farms.

The semi-autonomous Chinese territory of Hong Kong was the only non-European place mentioned. Mr Rosario said the others are Sweden, Britain, Austria, Ireland, Italy, Luxembourg, Poland, Romania, Slovenia, Slovakia, Denmark and non-EU member Switzerland.