"We have now established that more eggs from affected farms than previously identified came to the United Kingdom", the Food Standards Agency said in a statement, raising its estimate to 700,000 from 21,000.
Subsequent testing of eggs found them tainted with the banned insecticide, and around 180 Dutch farms have been locked down for testing.
It can cause damage to the liver, thyroid glands and kidneys, if consumed in large quantities, though this has only been tested on rats.
According to the Agency, in the United Kingdom infected mainly semi-finished products and processed products, where eggs are only one of many ingredients.
The likelihood of any related food illnesses from consuming contaminated products is very low.
"The number of egg products imported is very small".
Fipronil is commonly used in veterinary products to get rid of fleas, lice and ticks, but is banned by the European Union from being used to treat animals destined for human consumption, such as chickens.
The products that are being withdrawn by retailers include egg salads, sandwiches, mayonnaise and egg snack pots.
However, the Danish food administration urged calm, saying the eggs bought by Danæg Products posed no risk to human consumption.
In connection with the use of fipronil insecticide, the spokeswoman added, "There are several raids being held in The Netherlands, in conjunction with the Belgians".
Authorities suspect Belgian company Poultry Vision of producing a fipronil-laced treatment created to kill mites in chickens.
Following censure of this approach, Belgium launched a parliamentary hearing when Agriculture Minister Denis Ducarme said Belgian's food safety agency obtained an internal Dutch document that "supports the observation of the presence of fipronil in Dutch eggs at the end of November 2016".
The NVWA conceded that it received a tip-off in November past year but stressed there was "no evidence" of a food safety risk.
"All major United Kingdom retailers stock British Lion shell eggs and tests have shown that there is no risk from British eggs".
They have reportedly pinned the source of the issue to a supplier of cleaning products in the Netherlands.
The scare started in the Netherlands and Belgium and it is thought that Dutch disinfectant is at fault.
It also emerged on Thursday that two managers at a Dutch company had been arrested during joint raids by Dutch and Belgian authorities.
The UK Food Standards Agency said that the eggs were imported into the UK between March and June.