German health officials identified imported cucumbers from Spain Thursday as the source of a two-week E. coli O104 outbreak that has killed at least four people and made more than 100 others ill.

Three of four contaminated cucumbers analyzed by the Hamburg Institute for Hygiene and the Environment came from Spain, said the state health minister for Hamburg, Cornelia Pruefer-Storcks.

Cucumbers from the affected producers have been pulled from shelves and officials have told people to stop eating cucumbers. The country of origin of the other cucumber is not yet known.