Health authorities are investigating at least 34 egg producers in the states of North Rhine-Westphalia and Lower Saxony, but other states also appear to be connected and prosecutors in the state of North Rhine-Westphalia have opened an investigation.

Authorities quarantined around 1000 farms in Lower Saxony and Saxony-Anhalt on Monday to determine whether the dioxin levels there were higher than allowed.

In North Rhine-Westphalia, environmental officials said on Monday that 8,000 hens believed to have been contaminated had been destroyed as a precautionary measure.

Suppliers have been forced to suspend deliveries amid ongoing checks which have already uncovered samples containing dioxin at twice the allowed rate.

The toxic chemical, which has been linked to cancer and is stubbornly persistent once released into the environment, has been traced back to contaminated feed.

Authorities believe industrial fats were substituted for vegetable fats at some point in the tainted feed's manufacturing process.

State government officials across Germany are looking into the possibility that the poisonous fats may have made their way into other feed suppliers around the country.

On Friday, a government spokesman for the northern German state of Schleswig Holstein, Knut Peters, said the company Harles und Jentzsch had alerted authorities after discovering that vegetable oils used in the preparation of animal feed had become mixed with industrial oils.

"We detected the impurities ourselves during a routine test, and contacted the authorities immediately," Siegfried Sievert, production manager of the company told the Westfalen-Blatt newspaper. "So far we don't have an explanation."

Working together

What good is the stamp if there's dioxin inside

Sievert said his company was working closely with officials to establish how the dioxin, which can cause mid to long-term health problems if consumed in any quantity, found its way into the feed process in the first place.

Further test results are expected this week, but Peters said the public should refrain from passing judgement on the company before a proper investigation of the incident.

"As far as we are concerned there is no indication of a connection between the company and the dioxin-contaminated eggs," the government spokesman said.

The Minister for Consumer Affairs in North Rhine-Westphalia, Johannes Remmel, told a local newspaper that the contamination must either be the work of criminals or the result of extreme negligence.

Either way, he stressed the importance of finding the feed fats - or feed into which they may subsequently have been mixed - known to have been delivered to manufacturers in five German states.

"We cannot rule out that there are dioxin-contaminated eggs sitting on shop shelves," he said.

Author: Tamsin Walker, Gabriel Borrud (AP, dpa)

Editor: Nicole Goebel