German supermarkets were on Thursday afternoon pulling Spanish cucumbers off their shelves in response to the scare.
The contaminated vegetables were sold at a Hamburg market, Hamburg's Health Minister Cornelia Storck said.
Of four cucumbers found to be carrying the bacteria, three came from two separate Spanish suppliers while the origin of the fourth was unknown. One of the contaminated cucumbers was an organic product.
At least three people have died during the outbreak and other deaths are suspected to be related to the bacteria. Roughly 140 people are considered by health authorities to have been severely sickened during the outbreak. Most of the roughly 600 cases of E. coli reported so far have been centred in northern Germany, particularly in the Hamburg area.
The strain of E. coli gripping Germany is a particularly virulent one, said Helge Karch, a researcher at the University Hospital of Münster, whose team discovered the identity of the strain and is developing a test to more easily detect it.
The discovery is “an important step in the search for paths of transmission,” Karch said.
The public health authority, the Robert Koch Institute (RKI), encouraged people to avoid eating raw tomatoes, cucumbers and lettuce for the time being.
That prompted cafes and bakeries in the north of the country to abandon salad en masse, spurring a noticeable drop in vegetable sales on Thursday.
Kurt-Henning Klamoth, president of the German Farmers Federation (DBB) accused the media of scaremongering and condemned speculation that the illness has been spread through organic fertilizers.
Health officials cautioned that they were still looking for a definitive cause and emphasized that more deaths were likely.
“We must expect to lose patients," said University Hospital Hamburg-Eppendorf kidney specialist Rolf Stahl.
The country's largest supermarket chain, Metro – which operates Real, Metro Cash & Carry and Galeria Kaufhof – along with Kaiser's Tengelmann and the Rewe Group have all stopped sales of the vegetables.
Metro plans as a precaution to stock only cucumbers from other countries.
Discounter Aldi Nord said it doesn't normally stock Spanish cucumber anyway but it has taken other vegetables and fruits from Spain such as spinach leaves off its shelves anyway.
Aldi Süd, which operates in the south of the country, said it saw no need to take action for the time being because it did not believe any of its products were affected. Spain is Germany's second biggest supplier of cucumbers within the European Union, sending 179,500 tonnes of the vegetable to Germany in 2009, according to the Federal Office for Agriculture.
Meanwhile European Union officials expressed concern that the outbreak would soon spread beyond Germany's borders. The bloc was expected to soon declare a special alert, which would authorize EU members to take special action to protect their populations, such as putting restrictions on German vegetable imports.
“It's a matter of time until the hazardous E. coli pathogens jump to other EU countries,” European Parliament Committee for Health and Food Safety chairman Jo Leinen told the Neue Osnabrücker Zeitung.
As a pre-emptive measure, the bloc was expected soon to declare a special alert, which would authorize EU members to take special action to protect their populations, such as putting restrictions on German vegetable imports.
The latest death to be definitively linked to the outbreak was a 41-year-old woman from Cuxhaven on the North Sea. Hamburg health authorities said they were determining whether a 38-year-old man found dead in his apartment on Tuesday may have been killed by E. Coli.