The joint action comes a day after Belgium accused the Netherlands of knowing about the problem of fipronil in eggs since November 2016, but failing to inform them until July.

“There are several raids being held in The Netherlands, in conjunction with the Belgians,” Dutch public prosecution service spokeswoman Marieke van der Molen told AFP, but declined to give further details.

A spokeswoman for the prosecutor in Belgium’s northern port city of Antwerp said in a statement: “In connection with the fipronil case, several raids are currently being carried out.”

The Belgian searches took place at eight sites in the Flanders region of Belgium, near the border with the Netherlands, Het Laatste Nieuws newspaper reported.

Dutch and Belgian prosecutors earlier this month opened a fraud investigation into how fipronil, which can harm human health, got into the food chain.

The scandal has spread across eight European countries so far with authorities ordering the destruction of millions of eggs and supermarkets in several nations removing eggs from their shelves.

Fipronil is commonly used in veterinary products to get rid of fleas, lice and ticks but it is banned by the EU from being used to treat animals destined for human consumption, such as chickens.

In large quantities, the insecticide is considered by the World Health Organization to be “moderately hazardous” and can have dangerous effects on people’s kidneys, liver and thyroid glands.

The problem is believed to stem from a substance used by a Dutch company, Chickfriend, that farmers in the Netherlands and Belgium say they hired to treat their chickens.

A lawyer for a Belgian company, Poultry-Vision, says the firm sold it to Chickfriend but has not said where it got the substance.

The French government says a Belgian company — which it did not identify — mixed fipronil with another, lawful, substance. DM