Derwentside District Council closed down Robson's Fresh Foods shop in Stanley, thought to be the source of the outbreak, on 29 July.

Three people are being treated in hospital and there are a further 10 suspected cases.

The Outbreak Control Team said more cases were expected to emerge but people have been urged not to panic.

Contaminated food

Dr Deb Wilson, chair of the outbreak team, said investigations into the outbreak were continuing.

She said: "So far we have identified one possible link between Robson's Fresh Foods in Stanley and meat products.

"No other outlets have as yet been identified, but investigations are ongoing."

Dr Wilson said the owner of Robson's was co-operating fully with the local council.

She added: "Our advice to the public, as a precautionary measure, is to throw away any meat products which were purchased from Robson's Fresh Foods."

Salmonella usually occurs through eating contaminated food, usually of animal origin or through close contact with an infected person.

The outbreak is being investigated by Derwentside Primary Care Trust and the Health Protection Agency.