Cucumbers were back on the radar of German health authorities Wednesday as the possible cause of an E. coli outbreak in Europe that has killed at least 26 people and sickened over 2,700 others.

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 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's the source.

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

The father of the family had diarrhea, the mother was hospitalized 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 hospitalized for almost two weeks.

"The family was sick," 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. EU farmers claim losses up to $417 million a week as ripe produce rots in fields and warehouses.

The EU therefore increased its offer of compensation to farmers for the E. coli outbreak to $210 million, EU Farm Commissioner Dacian Ciolos said. A final decision will be made next week by EU member states.

Outside health experts and German lawmakers have strongly criticized the investigation in Germany, saying the infections should have been spotted much sooner and having state-by-state probes was hurting the search for a cause.

Reason for hope: German health minister

After authorities in Hamburg state had blamed Spanish cucumbers, Lower Saxony turned on sprouts which officials there say "is still the best lead we have."

But more tests came back negative Wednesday on sprout samples from an organic farm in the northern town of Bienenbuettel but the farm is still considered a possible source for the outbreak. German Agriculture Minister Ilse Aigner said eight clusters of patients — more than 50 infected people — can now be tracked to that farm.

"That means even if we have no [positive] sprout test results yet, we have indications based on tracking nutrition the affected people eat," she said. "We are even looking for more cases that can be linked to the farm."

In Madrid, Spanish farmers handed out 40 tons of fruit and vegetables to draw attention to their plight. People lined up for 100 metres along dozens of tables to snap up a wide and colourful variety of produce, including cherry tomatoes, lettuce, peppers, cucumbers and watermelons.

Germany's national disease control centre, the Robert Koch Institute, reported 300 more E. coli cases Wednesday, raising the total to 2,648. Another 100 E. coli cases are in other European countries and the United States.

Despite the new infections, German Health Minister Daniel Bahr said the overall trend showed fewer new cases of illness, and expressed cautious optimism.

"I cannot yet give an all-clear, but after an analysis of the numbers there's reason for hope," Bahr told ARD television.

The European Union health chief John Dalli also held an emergency meeting with German officials on the E. coli crisis but avoided publicly criticizing their efforts, saying the cucumber warning was justified" based on the data Hamburg authorities had at the time.