The Thuringia state agriculture ministry could not immediately be reached for comment. A spokeswoman for the federal agriculture ministry said the ministry was very concerned but did not confirm the figure of 1,000 tonnes.

Part of the feed was sold to a buyer in the Netherlands, where the agriculture ministry said last week that a buyer had imported 200 tonnes of possibly contaminated feed from the German feed maker rather than 100 tonnes as previously thought.

The Dutch ministry said in a statement it had banned 240 Dutch farms that used the feed from having their animals slaughtered and the meat sold for consumption.

"The minister thinks this ban is necessary, as long as it isn't clear whether the (feed) is contaminated with dioxin," the Dutch ministry said, adding it expected tests on possible contamination to be completed early next week.

Other known buyers are in Germany, one in the state of Bavaria, one in Saxony-Anhalt and three in Thueringen itself.

Two of the Thuringia buyers are also animal feed producers and used the tainted products to make more feed, the Thueringen state agriculture ministry said on Wednesday.

The ministry said this week the contamination levels were not considered a danger to health.

A baking process using damp wood chips as fuel has been identified as the cause of contamination at the producer of the original 250 tonnes, which was made in November and December last year.

The company has been ordered to stop using the process and is facing legal action, but is permitted to produce animal feed on a separate production line using a different process, she said.

(Additional reported by Otti Thomas in Amsterdam).