German authorities are now casting doubt over whether Spanish cucumbers caused the massive outbreak of a deadly bacterial infection that has left at least 16 dead.
Health officials in Hamburg are saying that the source remains unidentified.
It was thought that cucumbers from Spain were at the origin of the outbreak.
But Spanish officials have refused to accept the blame, saying it is still unclear exactly when and where the vegetables were contaminated.
A total of 16 deaths have now been linked to the outbreak, including a fatality outside of Germany. A woman died in hospital in Sweden after picking up the infection in Germany.
There are 36 cases of suspected E coli in Sweden, all linked to travel in northern Germany, authorities said.
A small number of cases have been reported in Britain, Denmark, France and the Netherlands, all linked with travel to Germany.
The German government has identified the pathogen as hemolytic-uremic syndrome (HUS), a serious complication of a type of E coli known as Shiga toxin-producing E coli (STEC), and said it had killed 14 people and made at least 329 ill.
The European Centre for Disease Prevention and Control (ECDC) said in a risk assessment that the HUS/STEC outbreak is one the largest in the world of its kind.
HUS affects the blood, kidneys and, in severe cases, the nervous system and can be particularly serious for children and the elderly. Some 60 cases of HUS are reported annually in Germany, the government said.
Oliver Grieve, spokesman for the University Medical Centre Schleswig-Holstein in north Germany, said his hospital had 82 cases of HUS and 115 confirmed E coli cases. He said the number of cases there had doubled within the past few days.
The northern port city of Hamburg alone has reported 488 cases of E coli since the outbreak began in mid-May and has 94 cases of HUS.
A hospital in the city said it was transferring patients with less serious illnesses to other clinics to cope with the flood of HUS patients.
Spain, meanwhile, said it was mulling taking action over Spanish cucumbers being blamed for the outbreak.
'There is no proof of this and so we will demand explanations from who has attributed this matter to Spain,' Diego Lopez Garrido, secretary of state for the European Union, told journalists.
Horticultural farms in the southern Spanish region of Andalusia have been losing €7-8m a day since German authorities linked the bacteria to Spanish cucumbers last week.
