European Commission agricultural officials say thousands of farms may have to be temporarily shut down and checked after animal feed tainted with a banned growth hormone was shipped across Europe.

German officials announced on Tuesday that at least 332 farms were being checked for traces of the hormone medroxyprogestrone acetate (MPA), which is suspected of causing infertility in pigs and humans.

Food safety scares have rocked farmers

While as many as 11 of the European Union's 15 member states are believed to be affected, the hardest hit appears to be Germany, especially pig farms in North Rhine-Westphalia and Lower Saxony regions.

Animals suspected of eating the tainted feed cannot be moved until tests have been done.

If the tests are positive, the animals will be culled.

Already eaten

However, the BBC's Chris Morris reports that officials admit that some contaminated pork has already been sold to meat processing companies and has almost certainly been eaten.

European scientists believe MPA can cause infertility in humans.

They doubt that the current levels of contamination pose a danger to human health - but they're not taking any chances.

Officials believe that more than 8,000 tonnes of feed contaminated with the hormone had been manufactured in the Netherlands, after a syrup containing it was purchased from a now-bankrupt Belgium-based firm, Bioland.

Soft drinks

Traces of the substance were also recently found at two soft-drink manufacturers in Belgium and Germany that had purchased the syrup from Bioland.

A criminal investigation has been launched.

In Denmark, the authorities have halted deliveries from four cattle farms that also received the same feed.

The European Commission's food and animal feed safety committee is discussing the issue on Tuesday.

Animal feed shipments to Belgium, Spain and France were also reportedly affected.

Hundreds of Dutch farms have also been temporarily closed for testing after receiving the feed.