A farm in northern Germany has been identified as the most likely source of many of the infections in the E. coli outbreak that has left 22 people dead.
The farm, producing beansprouts, is located in Uelzen, south of Hamburg, the epicentre of the outbreak that has also made more than 2,000 people ill.
German officials were awaiting results of tests on the farm's produce that would offer more conclusive proof.
The farm has been closed and Germans advised to stop eating beansprouts.
EU agriculture ministers are to hold an emergency meeting on Tuesday to discuss the outbreak and its effect on production, the EU presidency has said.
Hospitals overwhelmed
The agriculture minister for Lower Saxony, Gert Lindemann, said: "Further evidence has emerged which points to a plant nursery in Uelzen as the source of the EHEC cases, or at least one of the sources," he said.
Definite proof would depend on test results, but "a connection has been found involving all the main outbreaks".
The farm is about 100km (62m) south of Hamburg and supplies restaurants and markets in the city and neighbouring German states.
Mr Lindemann said the farm grows a wide variety of beansprouts from seeds imported from different countries.
The beansprouts include adzuki, alfalfa, broccoli, peas, lentils and mung beans, all grown in the nursery for consumption in salads.
Mr Lindemann said the sprouts produced there are grown in temperatures of about 38C, "which is ideal for all bacteria".
The farm's general manager, Klaus Verbeck, was quoted by the Neue Osnabruecker Zeitung as saying that he could not see how it was to blame.
"I can't understand how the processes we have here and the accusations could possibly fit together.
"The salad sprouts are grown only from seeds and water, and they aren't fertilised at all. There aren't any animal fertilisers used in other areas on the farm either."
The BBC's Stephen Evans in Berlin says the latest news may cause embarrassment to German authorities, who had earlier pointed to Spanish farms as the source of the outbreak.
More than 2,150 people in Germany have been infected by enterohaemorrhagic E. coli (EHEC) bacteria. Many have developed haemolytic-uraemic syndrome (HUS), which can be fatal.
Cases have been concentrated in Hamburg, with infections in 12 other countries linked to travel in Germany.
Twenty-one of the victims have died in Germany, and one person in Sweden.
Scientists say the new E.coli strain is an aggressive hybrid form toxic to humans and not previously linked to food poisoning.
German Health Minister Daniel Bahr said it was not yet safe to give the all clear.
"We still have to expect more cases of HUS. We continue to recommend that people do not eat raw tomatoes, cucumbers and lettuce in northern Germany," he said.
Mr Bahr said hospitals in northern Germany were overwhelmed by the outbreak, though he said medical workers were doing "everything necessary" to help patients.
Hamburg's senator for health, Cornelia Pruefer-Storcks, said there were indications the outbreak was slackening.
Doctors in the city's hospitals said a large number of patients were showing signs of improvement.
EU health ministers will discuss the outbreak at their meeting in Luxembourg on Monday.
