German health authorities investigating an outbreak of E.coli in Europe suspect cucumbers as being the possible cause of a new case.

Two weeks ago, investigators blamed cucumbers from Spain for the deadly outbreak and then later ruled them out as the source.

Then, the focus shifted to sprouts from northern Germany, but none that were tested turned out to be contaminated with the bacteria strain blamed for the outbreak.

Now suspicions have fallen on a cucumber of an unknown country origin that has sickened a family in eastern Germany.

The cucumber - the first food found to be contaminated with the strain that has sickened thousands - was in the family's compost, but there is no conclusive evidence that it is the source.

"It's unclear whether the cucumber infected the people, or the people the cucumber," Saxony Anhalt state's health ministry spokesman Holger Paech said.

The father of the family had diarrhoea, the mother was hospitalised for several days and their 22-year-old daughter is among about 700 people across Europe with a severe complication that can lead to kidney failure. She has been hospitalised for almost two weeks.

"The family was sick," Mr Paech said. "So, they could have contaminated the cucumber instead of the other way round."

There has been no reported evidence of humans contaminating vegetables, but the Federal Institute for Risk Assessment maintained that "the finding does not allow any conclusions" because the cucumber had been lying in the compost between May 19 and May 30.

Laboratory tests on other samples taken from their house and from shops where they usually buy their vegetables all tested negative for the bacteria, he added.

Consumers across Europe are shunning fruit and vegetables, and the German warning against eating cucumbers, tomatoes, lettuce and sprouts is still in place.