The World Health Organisation has expressed fears that BSE, or mad cow disease, may have spread beyond Europe.

So far all known cases have been reported in Europe, but WHO officials in Geneva said they were concerned that BSE-infected meat in animal feed may have been sold around the world.

The warning came as prosecutors in Paris began preliminary investigations into whether to bring manslaughter charges against British and French ministers over deaths linked to mad cow disease.

Earlier, the European Commission threatened to ban some German sausages because of fears they may be contaminated with BSE.

WHO says the infection may have been spread during the delay before European governments began taking measures to stop the sale of suspect meat and animal feed.

The panic over BSE has spread across Europe

A spokesman told the BBC that there was so far no proof of any cases outside Europe.

But if BSE were to take hold in developing countries lacking Europe's level of infrastructure to deal with an outbreak, the social and economic consequences would be devastating, the official said.

The WHO says it is looking to establish procedures to test for the spread of the disease by way of beef and animal feed imported from Europe.

It envisages a major international conference to discuss the issue next year.

UK hit hardest

In the UK, there was a 10-year gap between the disease first surfacing and the export ban on its beef imposed in 1996.

The UK has by far the biggest number of BSE cases in Europe, but the disease has also struck in France, Ireland, Portugal and Germany.

Eighty-seven UK citizens have died from the brain-wasting human form of the disease, variant Creutzfeldt-Jakob disease (vCJD). The UK has spent billions of dollars trying to contain BSE.

The WHO and other UN agencies are reviewing the scientific evidence linked to BSE and vCJD.

Legal moves

More cases of BSE are expected in Germany

The legal moves in Paris follow a lawsuit filed last month by families of two French victims of vCJD.

The families want manslaughter charges brought against British officials for allowing the export of suspect animal feed after banning it at home in 1989 - and against French officials for not stopping it.

In October, Lord Phillips' report in the UK's BSE inquiry criticised successive government ministers for repeatedly misleading the public about the threat to human health posed by mad cow disease.

'Heavy responsibility'

A UK spokesman pointed out on Friday that the report had decided there was "no criminal case to answer".

French relatives want ministers to stand trial

But in their writ the French families said that Britain bore a heavy responsibility for "authorising the mass export of animal meal, which they recognise as being the main source of contamination".

Several court cases over BSE have begun in the UK, but they focus on charges of negligence rather than manslaughter - a charge more difficult to prove.

Consumer panic

The French lawsuits deal with the deaths of 27-year-old man in 1996, and a woman who died at the age of 36 last February.

Concern over BSE has sparked consumer panic in France, prompting the government to ban meat and bone meal feed, take T-bone steaks off restaurant menus and institute a sweeping programme of health tests for cattle.

The European Union reacted to the growing anxiety earlier this month by ordering a blanket six-month ban on meat and bone meal in all animal feed, and calling for tests on all cattle older than 30 months from next July.

Unilateral bans

The threat to ban some German sausages comes after the first case of BSE in a German-born cow was announced in November.

German officials had until then claimed that the country's cattle were free from the disease.

Two new cases of BSE in Germany have now been confirmed, bringing the total to five, and more are now expected.

Several European countries have already slapped unilateral bans on German beef and they were joined on Thursday by Germany's neighbour, Austria - one of the few remaining EU countries to be free of BSE.