Germany says the number of its people sickened by a mysterious killer bacteria is growing rapidly.

The country's national disease control center Wednesday said the number of confirmed cases of people sickened by the food-borne bacterial outbreak jumped from 373 on Tuesday to 470 a day later. Fifteen people have died in Germany from the E. coli infections and another one in Sweden.

German Agriculture Minister Ilse Aigner said scientists have been working non-stop to pinpoint the source of the outbreak, but they have yet to find the cause. Several days into the outbreak, authorities say they are not sure what produce — and what country — is responsible, although those sickened most likely were infected by eating raw cucumbers, tomatoes or lettuce. She advised consumers to continue to avoid those vegetables. The E. coli infection attacks the victims' kidneys, sometimes causing seizures, strokes and comas.

Germany initially pointed to a few cucumbers from Spain as a possible source of the contamination, but further tests showed that those vegetables were not the cause of the outbreak. Germany, Belgium and Russia have banned Spanish vegetable imports, pending an investigation, but Spanish officials say those countries wrongly jumped to conclusions.

Spain said it is not ruling out taking legal actions against German officials who questioned the quality of the Spanish imports. The allegations have sharply curtailed Spanish fruit and vegetable exports.

The World Health Organization says that besides Germany and Sweden, cases of the infections have been reported in seven other European countries — Austria, Denmark, the Netherlands, Norway, Spain, Switzerland and Britain.