The Lau's Buffet King restaurant in Durham City has since closed

The rare strain of the infection was traced to Lau's Buffet King Restaurant, in North Road, Durham City, in May 2003. The restaurant has since reopened under another name and with new management.

At least 138 people were affected by the rare strain of Type-56 salmonella, with 13 of them admitted to hospital.

A report by the County Durham and Tees Valley Health Protection Unit into the incident has now been published.

It concluded it was "highly likely" the outbreak was associated with eating at the restaurant, but does not come to a firm conclusion about how the food came to be contaminated.

The report identified a number of factors including discovering that four members of staff were carriers of the bug, although they were not showing symptoms.

Two of the kitchen staff were new recruits and the report says "the food hygiene training of these two was not clear".

The co-ordinated efforts of the agencies involved quickly identified the outbreak and took effective measures to protect the public health Dr Tricia Cresswell, director of public health, Durham and Chester-le-Street Primary Care Trust

The report says investigators were hampered by a "significant difficulty" in interviewing staff for whom English was not their first language.

Other factors identified were the surface temperature of the food on display in the buffet was not high enough and some of the food-handling procedures could allow cross-contamination.

The restaurant was never prosecuted and the report said it did co-operate with the outbreak control team.

Details of the outbreak only became public in June, after it had been contained.

The report says informing the media and public would have been unhelpful and jeopardise the co-operation of the restaurant.

'Serious incident'

The study will go before the board of Durham and Chester-le-Street Primary Care Trust on Thursday.

Trust director of public health Dr Tricia Cresswell said: "The outbreak was a serious incident affecting a large number of individuals from the local area and the North East.

"The co-ordinated efforts of the agencies involved quickly identified the outbreak and took effective measures to protect the public health.

"The PCT, Durham City Council, other local councils, the Health Protection Unit and other individual agencies involved are considering the report and are committed to identifying learning points and recommendations to continue to strengthen local health protection arrangements."