Health officials say ten children and one adult have now been infected following an outbreak of E.coli at a North Yorkshire nursery.

Four of the children are in hospital after the illness was discovered at the Busy Bears Nursery in Skipton.

One of them is being treated for haemolytic uraemic syndrome which affects the kidneys.

The other six toddlers and a parent remain without symptoms.

Warning signs

The outbreak control team will continue to monitor the situation.

Parents have been asked to look out for the symptoms of the disease such as vomiting, diarrhoea, stomach pain, blood in diarrhoea and fever.

The incubation period can be nine days and parents have been told to keep their children inside and away from others.

The nursery has been closed and all 23 staff and 143 children are being screened for signs of infection.

Investigations

Dr Ebere Okereke, consultant for communicable disease control in North Yorkshire, said: "The nursery closed, not because there is anything wrong with the nursery, but to prevent the children spreading it between them.

"Young children are not good at washing their hands and so by closing the nursery we are reducing the risk of the children spreading the bug, one to another."

E.coli 0157 is the most serious form of the food poisoning bug and can lead to acute kidney failure.

Environmental health teams are trying to locate the source of the outbreak.

An investigation by the local environmental health unit later concluded that the source of the outbreak was "outside the nursery." It found the infection was introduced into the nursery where it was spread by person to person contact. A spokesman told the BBC they were "generally happy with standards at the nursery." They also recommended that nurseries should have "a clear exclusion policy for children with gastrointestinal symptoms and these should be rigorously applied." This guidance has been issued to all playgroups and nurseries in North Yorkshire.