An E. coli outbreak, which is linked to contaminated cucumbers that has killed 14 people and made more than 300 seriously ill in Germany, has spread to other north European countries, Reuters reported.

The source of the powerful bacteria is unknown, German authorities said on Monday ahead of a crisis meeting of federal and state officials in Berlin. Most of the deaths have been in northern Germany as reported by Reuters.

Austrian authorities has sent inspectors to supermarkets to make sure that Spanish vegetables, which might be suspected of any contamination, are removed.

In Italy, they have been on inspecting since Saturday for any contaminated imports from Spain, the Netherlands or any other European country.

The E. coli pathogen has been identified on cucumbers imported from Spain, but it is unclear if they were contaminated there, during the transport or in Germany.

A number of cases have been reported in Britain, Denmark, France and the Netherlands, all linked with travel to Germany.

Thirty-six cases of suspected E. coli in Sweden, also linked to travel in northern Germany, authorities said.

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, Reuters reported.

HUS affects blood, kidney, in severe cases, the nervous system and can be particularly serious for children and the elderly.

The northern port of Hamburg alone has reported 488 cases of E. coli since the outbreak began in mid-May.

Meanwhile, Spain said on Monday it was considering of taking action against the “Spanish cucumbers” being blamed for the outbreak.

Sweden, on the other hand, has advised Swedes travelling to north Germany to steer clear of cucumbers, tomatoes and salad.

The outbreak has forced Russia to ban imports of some fresh vegetables from Germany and Spain.

German authorities have warned consumers to avoid eating lettuces, cucumbers and tomatoes and have ordered some products to be removed from store shelves.

As long as the experts in Germany and Spain have not been able to name the source of the agent without any doubt, the general warning for vegetables still holds, German Consumer Protection Minister Ilse Aigner had said on Sunday.