Authorities in Europe have yet to pin down the source of a killer E. coli pathogen that has been spreading from northern Germany for weeks.

German health officials said Saturday that authorities were scouring a restaurant in Lübeck, a port city on the Baltic Sea, where several guests who had eaten at the "Kartoffel-Keller" were reported to have contracted the rare bacteria.

Lübeck is now at the center of the E. coli controversy

"It was like a blow to the head when I heard the news," proprietor Joachim Berger said after his restaurant was inspected by Lübeck authorities.

The Lübecker Nachrichten newspaper said scientists had identified the local restaurant as a potential place where the bacteria could have been transmitted.

The report said 17 people who had dined there had come down with the bug, including one who has since passed away and a group of eight Danish tourists.

Intercontinental outbreak

The outbreak is the biggest epidemic caused by bacteria in recent decades in Germany. All but one of the 20 fatalities have occurred in the country, and the other victim, a patient who died in Sweden, had recently returned from Germany.

Thus far, the infection has also been reported in Austria, Britain, the Czech Republic, Denmark, France, The Netherlands, Norway, Spain, Sweden, Switzerland and the United States. In each of the cases, those infected said they had recently travelled to Germany.

Regional German health authorities have reported more than 2,000 cases of people falling ill, with symptoms including stomach cramps, diarrhea, fever and vomiting.

The World Health Organization has identified the bacteria as a rare strain - enterohaemorrhagic E. coli (EHEC) - never before connected to an outbreak of food poisoning. But researchers in Hamburg said earlier they and Chinese colleagues had found the strain was a "new type" that is extremely aggressive and resistant to antibiotics.

Trade rows

The ongoing health crisis has also triggered a food scare that has strained trade relations in Europe.

Rows of EU vegetable produce are going unsold

The first dispute was between Spain and Germany, after Hamburg authorities attributed the mystery E. coli strain to cucumbers imported from Spain. When that warning emerged as a false alarm, Madrid said it wanted compensation from Germany and the EU for sales losses and slander.

At this point, tens of thousands of tons of Spanish produce have been unsold, costing Spanish growers an estimated 200 million euros ($290 million) a week.

The row widened when Russia imposed a ban of all vegetable imports from the entire EU, a move criticized by the bloc's executive as "disproportionate" and even detrimental to Moscow's aspirations for World Trade Organization membership.

Russian Prime Minister Vladimir Putin immediately rejected the criticism and said the Kremlin - which imports some 600 million euros of EU vegetables per year - would only discontinue the ban after the source of the outbreak had been determined.

Author: Gabriel Borrud (AFP, Reuters)

Editor: Andreas Illmer