THE number of casualties of an outbreak of the food bug salmonella rose yesterday - and health officials said more cases were likely.

Last night, seven people were diagnosed with the infection, taking the number of cases to 28. Another 11 suspected cases are being monitored.

Investigators believe the possible source of the outbreak is meat sold at Robson's Fresh Foods, in Stanley, County Durham.

Dr Deb Wilson, chairman of the Health Protection Agency's Outbreak Control Team, said the team wanted to reassure people that effective measures had been put in place.

"However, we anticipate that further cases of salmonella, in people who may have eaten contaminated food before the control measures were put in place, will come to light over the next week," she said.

More cases are expected because of the delay between people becoming ill and contacting their GP, she said.

One person affected was in hospital last night, but their condition was not thought to be serious.

Laboratory staff raised the alarm last Thursday and the owner of the Robson's Fresh Foods store, in Front Street, closed the outlet that afternoon, after Derwentside District Council issued an emergency prohibition order. The proprietor is co-operating fully with the team's inquiry.

Salmonella can cause a range of symptoms, including fever, vomiting, headaches, abdominal pains and diarrhoea.

Patients can become infected by either eating contaminated food, or through close contact with an infected person or animal.

Dr Wilson urged people to throw away any meat products bought from Robson's Fresh Foods. Anyone who has severe diarrhoea lasting more than 48 hours is asked to contact NHS Direct on 0845 4647, or their GP.