It can cause damage to the liver, thyroid glands and kidneys, if consumed in large quantities, though this has only been tested on rats.
The food regulator claimed on Monday that only 21,000 had been imported from implicated farms.
Luxembourg became the latest European country hit by a scare over tainted eggs, with a major supermarket chain pulling them from the shelves and other firms affected, authorities said Thursday.
It emerged today that this was a false assurance and that potentially contaminatedproducts were still being...
The FSA said the 700,000 eggs now in the food chain mainly affected processed food in which egg is one ingredient among many, such as in sandwich fillings or chilled foods.
The number of egg or egg products imported is very small.
The contamination scare became public on 1 August when it was revealed that tests had found that fipronil, which is banned across the European Union from use in the production of foodstuffs, had found its way into the food chain. Some eggs were sent back, while others were used in minced meat and luncheon meat.
"This is just the latest of a number of food safety issues connected to eggs produced outside of the United Kingdom in recent years".
"The Dutch investigation focused on the Dutch company that allegedly used Fipronil, a Belgian supplier as well as a Dutch company that colluded with the Belgian supplier", said a statement released on Thursday morning.
The Agency put out its statement following an investigation into the problem, establishing that many more eggs than it previously believed had come into the United Kingdom from the affected farms.
However, ChickFriend, a Dutch company, is under investigation for buying the product and treating poultry farms in both Belgium and the Netherlands, according to numerous media reports.
Farmers in the Netherlands - one of Europe's biggest egg exporters - and Belgium have previously identified Chickfriend as the company that they hired to treat their chickens to eradicate the parasite red lice.
The arrests came after coordinated raids with Belgian authorities at eight locations across The Netherlands with the assistance of Europe's policing and judicial agencies Europol and Eurojust.
Waitrose, Sainsbury's, Asda and Morrisons are all recalling the egg-containing products, although the agency said that some of the recalled products will have already been consumed.
Mr Ducharme added: "If we had seen this information communicated to our respective agencies, vigilance concerning Fipronil would have been greatly increased".
Dutch health authorities have denied that they knew about the issue in November.