Police have begun an investigation into how contaminated feed found its way on to 47 farms in the Irish Republic.

Millstream Power Recycling, which recycles food into pig meal, is thought to be responsible for the potentially harmful level of dioxins found in the feed which reached up to 200 times the legal limit.

Officials are testing oil put in a machine that was used to dry animal feed.

A spokesman for the company said a full investigation would be carried out.

Suspicions were first raised last week (1 December) when a routine test on pigs indicated a presence of polychlorinated biphenyls (PCBs) – banned in the Irish Republic since the 1970s – in the animal feed.

Northern Ireland has also been affected as nine farms there were supplied with the same feed.

As a result, supermarkets across the UK have withdrawn pork produced in the Irish Republic and Northern Ireland since September, following official advice.

Despite the mass recall of products, food safety authorities in Britain and Ireland have reassured consumers that the public health risks are low.

The Food Standards Agency (FSA) said it was advising consumers not to eat Irish pork until an investigation into whether contaminated products had been distributed in the UK.

Dioxins are formed during waste incineration and during some industrial processes. They are normally found in low levels but some are highly toxic and can cause cancer and damage to reproductive and immune systems.

But the FSA said it did not believe there was a significant risk to UK consumers.

Padraig Walshe, President of the Irish Farmers’ Association, told the BBC that the pig feed contamination was a “huge blow to Irish farming”.

But Mr Walshe was quick to absolve Irish farmers of any blame.

“No farmer did anything untoward,” he said. “The animals on those farms will probably be disposed of but those farms have been isolated since the middle of last week.”