Beansprouts grown in north Germany are one of the likely sources of the E.coli outbreak that has killed at least 21 people in Europe in the last two weeks.
Conclusive results will not be available until Monday.
German investigators had originally targeted a shipment of Spanish Cucumbers.
Gert Lindemann, the Agriculture Minister for the German state of Lower Saxony, said there was a clear connection between those who contracted the bug and the food establishments that received shipments of beansprouts.
He said: “The trade connection shows again and again the link between this producer and cases of the illness.”
German federal Health Minister, Daniel Bahr, said hospitals in northern Germany were overwhelmed by the outbreak but everything was being done to help patients.
Bahr visited the University Medical Centre in Hamberg-Eppendorf to see the situation first-hand and talk to staff who had been working around the clock.