Discount supermarket giant Aldi said Friday it was pulling all Dutch eggs from its shelves in Germany over an insecticide scandal that has spread to food stores across Europe.

Aldi said it was making the move "purely as a precaution" but acknowledged it could lead to "market shortages" for eggs in Europe's top economy.

Authorities in Belgium, Switzerland and Sweden also said they were tracking shipments and removing eggs, as the impact of the affair widened.

Aldi pulled all of the Dutch eggs after it emerged that at least three million tainted with a toxic insecticide had made their way to Germany and been sold.

However a regional agriculture minister, Christian Meyer of Lower Saxony, told ZDF public television Friday that it was now believed 10 million contaminated eggs might have reached Germany.

Authorities suspect the substance, fipronil, was introduced to poultry farms by a Dutch business named Chickfriend that was brought in to treat red lice, a nasty parasite in chickens.

In large quantities, the insecticide is considered "moderately hazardous" according to the World Health Organization, and can be dangerous to people's kidneys, liver and thyroid glands.

In Belgium, the Colruyt supermarket said it had removed eggs from two suppliers in July, whose farms were suspected by safety monitors of being contaminated with insecticide.

The country's food safety agency (AFSCA) said they had seized eggs before they reached the shelves and deployed "field agents to verify that the necessary measures at the farms are applied".

- 'Public health at stake' -

Dutch and Belgian media reports that the substance containing the insecticide was supplied to Chickfriend by a Belgian firm have not been confirmed.

However AFSCA said a criminal probe, in cooperation with prosecutors, had been launched.

Eggs were also withdrawn by supermarkets in Switzerland, but the authorities who approved the recall urged people not to panic. 

"The quantities observed so far do not endanger the health of consumers," said the Swiss Food Safety Authority (OSAV).

Sweden's food safety safety agency said one batch of contaminated eggs had been delivered to a small wholesaler.

The European Commission is following the case very closely, as issues of public health are at stake, said spokeswoman Anna-Kaisa Itkonen.

With losses expected to run into millions of euros (dollars), it is another blow for Dutch poultry farmers after 190,000 ducks were culled in November amid a highly infectious strain of bird flu.

Marieke van der Molen, spokeswoman for the Dutch public prosecutor's office, said a criminal investigation had been opened to determine the source of the contamination. 

Belgium's federal food chain security agency (AFSCA) has also launched a criminal probe in cooperation with prosecutors.