German officials closed a primary school in the west of the country on Tuesday after a number of students fell ill with E.coli O104 responsible for an outbreak that has killed 48 people.

The school in the town of Altenbeken will be shut for a week, about the length of the E. coli incubation period, to prevent a possible spread of the bacteria, local officials said.

So far more than 4,000 people in Europe and North America have been sickened by the bacteria, with all the cases so far traced to travel in, or produce from, northern Germany. The rate of infection has slowed considerably since its climax in May.

Health authorities have pinned the outbreak to contaminated vegetable sprouts and shoots, of the type eaten in salads, from an organic farm near Hamburg.

Health officials responsible for Altenbeken believed poor hygiene by both students and school canteen workers caused the spread of the bacteria, rather than contaminated bean sprouts.