A further 12 people are suspected of having the bug, which has been linked to a food shop in Stanley.

Health officials say there are 51 confirmed cases, with four people in hospital.

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

'Control measures'

The authority's Outbreak Control Team said more cases may still emerge, but have urged residents in the area not to panic.

Dr Deb Wilson, chair of the outbreak team, said: "We would like to reassure the public that effective control measures have been put into place.

"However, we anticipate that further cases, in people who may have eaten contaminated food before the control measures were put in place, will continue to come to light over the next few days.

"Our findings so far continue to support a possible link with Robson's Fresh Foods.

"The proprietor is continuing to co-operate fully with Derwentside District Council."

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