New data shows that beansprouts are the most likely source of the outbreak of E coli that has killed 30 people so far.
More than 1,000 sample tests focusing on beansprouts have been taken so far.
Although none of the samples have tested positive yet for the bacteria, Germany's centre for disease control said studies could identify them as the source.
'It's the beansprouts,' Reinhard Burger, head of the Robert Koch Institute, told a news conference.
The investigation has focused on an organic beansprout farm in the northern state of Lower Saxony, which has been shut down.
The vegetables are popular in Germany, where they are served in most salad bars and often in sandwiches.
More than 3,000 people have so far fallen ill with what starts as stomach bug symptoms.
They face uncertainty over whether they will develop haemolytic uremic syndrome (HUS), which destroys red blood cells and causes severe kidney problems.
'It is very satisfying to present this discovery today, to be able to isolate the cause and source of the infection,' Mr Burger added.
'It is the result of intensive cooperation between German health and food authorities.'
'People who consumed (bean) sprouts were nine times more likely to have bloody diarrhoea than those who did not,' Mr Burger said.
'The outbreak is not over,' he added.
Russia lifts vegetable ban
Meanwhile, Russia has agreed to lift its ban on vegetable imports from the EU, European Commission President Jose Manuel Barroso said.
‘We are happy that we have agreed that the ban on vegetables from the European Union will be lifted,’ Mr Barroso told a news conference after an EU-Russia summit.
The Russian import ban had threatened to overshadow the summit, with the EU describing it as disproportionate and not justified by science.
Russian President Dmitry Medvedev told the news conference his country would resume vegetable imports if European Union agencies provided safety guarantees.