THE strain of E-coli involved in a major outbreak which caused the death of a child has not been detected in the blue cheese suspected of being the source of the bug, food safety officials say.

The revelation comes as a Crown Office investigation was launched into the death of a three-year-old girl during the E-coli outbreak which has been linked to Dunsyre Blue.

The child, who has not been named and is from the Dunbartonshire area, is one of 20 people who were infected with the potentially deadly bug in July.

Food safety watchdog Food Standards Scotland (FSS) had said Dunsyre Blue, which is made from unpasteurised cow's milk, was the "most likely" cause of the outbreak, as a number of those affected are thought to have consumed the cheese.

However in response to a question from the Sunday Herald asking if any tests had pinpointed Dunsyre Blue as the source of the E-coli outbreak, the FSS said: "Testing carried out to date from samples taken by South Lanarkshire Council as part of this investigation have not detected the same strain linked to the outbreak.

"Testing is still ongoing and we will ensure that appropriate action where necessary is taken to protect consumers."

Lanark-based manufacturer, Errington Cheese, has strongly disputed the link and said its own extensive testing has suggested its product was not the cause.

The row deepened further yesterday after the FSS issued a recall over a fourth batch of cheese produced by the manufacturer – Lanark White – which it said "may contain E-coli bacteria". It said a sample had tested positive for E-coli 0157 and was a "potential risk to health".

The recall involves a batch G14 of Lanark White, made from unpasteurised sheep's milk, which was on sale between 22 August and 10 September.

It ordered local authorities to ensure it is removed from the market and destroyed after the firm refused to instigate a voluntary recall. The statement added: "FSS and South Lanarkshire Council's investigations into food safety related to unpasteurised cheese produced by Errington Cheese are ongoing."

However the company said it had concerns about the way these investigations had been carried out and was awaiting the results of its own tests due tomorrow.

It added: "We have given careful consideration to this and to the fact that the cheese has been on the market for three weeks now with absolutely no reported incidence of illness.

"We have arranged for the sample of the same cheese tested by the authorities to be tested and the results will be ready on Monday, when we will review the situation and post an update."

Professor Hugh Pennington, the country’s leading expert on E-coli, said it could be difficult to identify it in any product suspected of causing food poisoning as by the time the illness comes to light, the food is usually all consumed or thrown away.

"Even if some of the batch (of food) is available for testing the bug might not be evenly distributed through a whole product, and so you might test part of the product that has been left or not been eaten yet and not find it – that doesn’t prove it wasn’t there in the bit that has been eaten," he said.

"Scientifically it is sometimes quite complicated to come to a straightforward conclusion. The cheese manufacturers rightly say what is the evidence – but the regulatory authorities might never be able to come up with that."

The sale of raw milk was banned in Scotland in 1983 following concerns over links to food poisoning outbreaks, although it can be sold elsewhere in the UK.

FSS advises that vulnerable groups, including pregnant women, children and the elderly should not consume raw unpasteurised milk, and dairy products such as cheese made from unpasteurised milk, due to the increased risk of food poisoning.

In 1995, Humphrey Errington, the founder of Errington Cheese, won a costly court battle against the now-defunct Clydesdale District Council over allegations his raw ewe’s milk cheese Lanark Blue was unfit for human consumption after attempts to blame it for an outbreak of listeria poisoning.

Joanna Blythman, investigative food journalist and the Sunday Herald's food critic, said she believed there was a prejudice in Scotland against raw milk products.

“The (Dunsyre Blue) case puts a chill round everyone who wants to make a small scale artisan food,” she said. “Meanwhile, the real prime suspects for large scale food poisoning are our industrial food producers.

“You feel there is a much bigger risk in terms of the amount of food consumed and the scale of the risk attached to other categories of food like chicken and pork, which people are buying every day. But there is always this idea the artisan is the problem.”

Shane Holland, executive chairman, of campaign group Slow Food in the UK, which champions local produce, pointed out that many renowned Continental cheeses – such as Camembert, Roquefort and Parmesan – are made from unpasteurised milk.