Three young calves on a Welsh farm have tested positive for BSE in what is believed to be the first cluster of infections discovered for almost a decade.

The Department for Environment, Food and Rural Affairs confirmed that experts were trying to establish whether the cows, from an unidentified farm in the Dyfed area, had become infected by the same route, possibly through feed imported from abroad.

The cows are aged between 36 and 43 months. The first case was identified more than two months ago and the two others were confirmed at the end of last week.

A Defra spokesman could not confirm reports that it is the first time three cases born after 1996 have been linked to one farm and that the three-year-old cow is the first BSE case born as late as 2002 in Europe.

BSE or "mad cow" disease sparked food safety fears in the early 1990s, with hundreds of thousands of animals destroyed. British beef remains banned in 84 countries and the country's produce is still officially considered "high risk".

The Defra spokesman said that cases of BSE were dropping "dramatically", falling by around 50 per cent a year.

"Active surveillance", whereby animals which have apparently died for reasons other than BSE are examined for the disease, has helped to boost detection.

Only 309 cases of BSE were reported last year, compared with more than 36,000 in 1992.

Alan Morris, the spokesman for the Farmers’ Union of Wales, said it was important that consumer confidence was not undermined by the latest discovery.

He said: "We don’t think consumers have anything to fear because the system in force is working to detect and remove cattle before they enter the food chain. There is no reason for consumers to be alarmed."

The deaths of about 140 people in the UK have been linked to variant CJD, a neurological disorder associated with eating BSE-infected meat.

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