Russian officials are refusing to back down on a total ban on all vegetables from the European Union as the continent's E. coli outbreak claims more victims.

Russian President Dmitry Medvedev and other top officials are hosting top EU officials for a two-day summit in the Russian city of Nizhny Novgorod starting Thursday.

Russia outraged EU leaders when it banned vegetables from EU member states last week. Russian Prime Minister Vladimir Putin has said Moscow will not lift the ban until the EU provides details on the source of the outbreak.

Authorities have so far failed to find where the bacteria originated, which has killed at least 29 people and sickened more than 2,800 others. Nearly all of the victims live in or visited northern Germany.

Russia is one of the EU's largest markets for vegetables and other produce.

Some critics charge Russia is using the E. coli outbreak as political leverage in order to gain membership in the World Trade Organization and achieve other political goals.

Russia has gained the support of the EU in its lengthy bid to join the world trade body, but outstanding issues between the two sides remain, including rules on food imports.

Officials also are expected to discuss a new EU-Russia cooperation agreement on trade, energy and investment, the global economy and developments in North Africa and the Middle East.

European Commission chief Jose Manuel Barroso and EU President Herman Van Rompuy are among the EU officials attending the summit.

Meanwhile, German investigators have ruled out home-grown organic sprouts, as well as lettuce, tomatoes and cucumbers from Spain as the cause of the E. coli outbreak.

Spanish Agriculture Minister Rosa Aguilar has been demanding full compensation from Germany for losses suffered by farmers in her country.

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.

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

Separately, the Associated Press reports Dutch authorities recalled red beet sprouts Thursday.

Officials said the sprouts were contaminated by a less deadly strain of the E. coli bacteria. There were no immediate reports of illness.