Belgian firm, which had in turn imported materials from Ireland.

"This is the sort of thing which starts off quite small and that then triggers off a broader contamination," European Commission spokeswoman Beate Gminder told a news conference.

"After a first case we have a second and a third and fourth etcetera...This is the sort of thing that can spread," she said.

Gminder said there had been deliveries of live pigs to Italy, Spain and France and possibly the shipment of processed products to the United Kingdom and Luxembourg.

The Commission has already asked the Dutch to stop output at farms and feed producers suspected of being contaminated with the MPA, or Medroxyprogesterone-acetate, hormone.

MPA is banned in the EU as scientists believe it might cause infertility in humans. Products containing it must be destroyed.

MPA is still used by humans in birth control pills and also in hormone replacement therapy for women going through menopause. It is approved as a growth stimulant in the United

States, Australia and New Zealand.

The Netherlands said it has launched a criminal investigation into how the feed became contaminated.

The world's third-largest exporter of pork, the Netherlands also said the number of farms affected had ballooned to 355 from 42 last week.

Belgium has arrested one of the owners of the bankrupt Belgian firm and is seeking the second. It says that Ireland should have informed it that pharmaceutical waste was being

shipped to the Belgian firm for processing.