Belgian authorities have admitted they began investigating pesticide contamination in eggs in early June - several weeks before the public was made aware of a food safety scare affecting several European countries.

Supermarkets have pulled millions of eggs from shelves after pesticide Fipronil was found in Dutch and Belgian poultry farms.

Kathy Brison, of the Belgian food safety agency, said that a Belgian farm alerted authorities to a possible contamination in June, and they began investigating and alerted Belgian prosecutors.

German authorities are frustrated by the apparent delay in informing European neighbours.

German Agriculture Minister Christian Schmidt plans to speak to his Belgian counterpart about the issue tomorrow.

Ms Brison said Belgian authorities thought it was an isolated incident and did not realise the scale of the problem until late July.