New data released in Germany strongly suggests that locally produced bean sprouts were, as suspected, the source of the deadly E. coli outbreak."It's the bean sprouts," said Reinhard Burger, head of Germany's centre for disease control.
"People who ate sprouts were nine times more likely to have bloody diarrhoea than those who did not," he added.
Officials initially blamed the E. coli, which has killed 29 people, on imported cucumbers, then bean sprouts.
Mr Burger warned the outbreak was not over.
It has generated a crisis for EU vegetable-growers, with Spanish cucumber producers wrongly blamed for the contamination.
Mr Burger, who heads the Robert Koch Institute, told reporters on Friday that even though no tests of the sprouts from a farm in Lower Saxony had come back positive, the epidemiological investigation of the pattern of the outbreak had produced enough evidence to draw the conclusion.
The institute, he added, was lifting its warning against eating cucumbers, tomatoes and lettuce, but keeping it in place for the sprouts.
Some 3,000 people have been taken ill with the German outbreak of E. coli, which involves a previously unknown strain of the bacterium.
Sufferers may develop haemolytic uraemic syndrome (HUS) where bacteria attack the kidneys and nervous system, giving them fits and often forcing them on to dialysis.
'Hot lead' Germany's top disease control official said the origin of the contamination was still believed to be the small organic farm in Lower Saxony which first came under suspicion at the weekend.
"The links are ever clearer - it's a hot lead," he said.
He said it was possible that all tainted sprouts had now either been consumed or thrown away, but he warned the crisis was not yet over.
"There will be new cases coming up," he said.
"Thousands of tests carried out on tomatoes, cucumbers and lettuce have proved negative," he added, speaking in Berlin at a joint news conference with the heads of Germany's federal institute for risk assessment and federal office for consumer protection.
Lower Saxony agriculture minister Gert Lindemann said earlier this week that experts had found no traces of the E. coli bacterium strain at the Bienenbuettel farm but he did not rule it out as the source of the contamination.
In an interview to be published in next week's edition of Focus magazine, Mr Lindemann said some 60 of the people taken ill had eaten sprouts from the farm, which employs about 15 people.
Contamination might have been caused by contaminated seeds or "poor hygiene", he added.