German authorities say the death toll from one Europe's worst E. coli outbreaks is up to at least 26.

They say more than 2,600 have been sickened since late May as a result of the mysterious bacteria. Nearly all the victims live in or visited northern Germany.

Authorities have failed to find the cause of the outbreak.

Overturning initial suspicions, German investigators have ruled out home-grown organic sprouts, as well as lettuce, tomatoes and cucumbers from Spain. Spanish Agriculture Minister Rosa Aguilar is demanding full compensation from Germany for losses suffered by farmers in her country.

Spanish farmers whose revenue has been hard-hit by the outbreak, on Wednesday gave away some 30 tons of fruit and vegetables to people in Madrid.

After heated discussions Wednesday, EU Farm Commissioner Dacian Ciolos raised his aid package offer to $306 million to help farmers recoup some of their losses from unsold vegetables because of the E. coli crisis. He had initially proposed $220 million in aid.

Russia and some other countries have banned all vegetables from the EU.

Russia is expected to address the E. coli outbreak Thursday,as part of a two day summit with EU leaders in Nizhny Novgord, Russia.

E. coli symptoms include stomach cramps, diarrhea, fever, vomiting, and in extreme cases kidney failure and death.