By Jo Revill, Juliette Jowit and Anushka Asthana

Guardian New Service: Research plant is near infected farm. Ban on export of British livestock.

An accidental leak from a scientific research laboratory was being investigated last night as the possible source of Britain's new foot and mouth disease outbreak. The news came as the government attempted to avert a full-scale crisis in farming and the tourism industry.

Movement of all livestock has been banned, exports to Europe stopped and country fairs cancelled to minimise the risk of the country suffering a disastrous rerun of the 2001 foot and mouth epidemic which cost the nation GBP8.5bn.

By last night, dozens of vets and farm officials had been sent into a 10km 'surveillance' zone around the outbreak centre at Woolfords Farm near Guildford in Surrey to start disinfecting equipment and vehicles, as well as testing sheep, cattle and pigs from other farms. Hundreds more cattle, sheep and pigs in the zone face slaughter amid fears that they may unwittingly have been infected by an airborne strain of the virus escaping from a nearby research centre.

Less than three miles from the farm is the Institute for Animal Health, at Pirbright, a government lab which is a European centre of animal disease testing. On the same site, there is a private vaccine research company, Merial SAS. The two are licensed by the government to work in conditions of maximum biosecurity and are independently monitored.

The inquiry is to see if the virus could have escaped within the past three weeks from either facility, either accidentally or deliberately, and been blown on the wind into Woolford Farm. Ironically, it is at the Institute that the virus from Woolfords farm is being tested, to see if there might be a vaccine available to protect other herds from the particular strain.

At a press conference in London, the government's chief veterinary officer, Debby Reynolds, said one of her first acts was to review biosecurity at Pirbright. There was an 'urgent investigation' into the origins of the virus and where it might have spread. 'At this early stage the evidence doesn't enable me to favour any hypothesis. It's important not to rule out any factor.'

She added: 'We're focusing on all possibilities - legal, illegal, lab-based, deliberate release - all those possibilities will be investigated and I wouldn't want to put any undue emphasis on any of those.'

Yesterday the Prime Minister, Gordon Brown, and the environment secretary, Hilary Benn, broke off their holidays to hold two emergency Cobra meetings to discuss the outbreak. Brown signalled his determination not to close off the countryside - which six years ago cost Britain more than GBP8bn and led to the slaughter of some 10 million animals.

Workers began culling infected cattle from Woolfords Farm where Derrick Pride was first told by vets on Thursday night that his herd might have foot and mouth. 'We will be doing, night and day, everything in our power to make sure that what happens happens quickly and happens decisively in a way that can reassure people that everything is being done,' the Prime Minister said. 'Our first priority has been to act quickly and decisively. That is why we have a national ban already imposed on the movement of sheep and pigs and cattle. That is why we have acted to create exclusion zones that are already in existence.

That is why also the culling of the herd in the infected area is already taking place.'

Opposition Conservative leader David Cameron also postponed his holiday in Brittany, France, to talk to farmers in his Oxfordshire constituency. He also talked to the Prime Minister to ascertain the measures that were being taken.

Richard Macdonald, head of the National Farmers' Union, said the news was 'pretty devastating' but praised Defra's quick response. He appealed to farmers to help contain the disease: 'If you do a cracking good job that will increase the prospects of containing it to a small area.'

The case at Woolfords is the first in Britain since 2001, when an epidemic of foot and mouth disease devastated farming. Many animal carcasses were burned on huge pyres that dotted the country. Swaths of countryside were declared off-limits to visitors, damaging tourism. This time, ministers have decided, there will be no pyres. The bodies of the first infected cattle were sent instead to an incinerator.

Tomorrow, the European Commission will decide what steps to take to limit any spread of the disease, but an automatic ban on livestock imports from the UK is now in place, under trade rules. An emergency meeting will be held in Brussels to look at restrictions on movement of animals and dispatch of food products from the UK.

Yesterday, Northern Ireland banned movement of animals from mainland Britain, as Stormont ministers drew up a document covering every possible scenario following the outbreak in Surrey. Scotland started to feel the knock-on effects of the ban on moving livestock. Three big agricultural shows in Scotland taking place this weekend are still going ahead - without cows, sheep and goats.

In the heart of the 10km 'surveillance zone' is Oxenford farm, in between Elstead and Milford, close to Pride's home. Yesterday, the owners were waiting nervously for news about what would happen to their livestock. Meanwhile, all farmers were urged to look for symptoms in their animals, which include shivering, lameness and telltale blisters on the foot and in the mouth. The virus is contained in fluid within the blisters, but can also be exhaled or carried in urine and dung.

If the source of the outbreak was Pirbright and all local livestock were to be culled 'it would be devastating,' said one woman at the farm who asked not to be named.

Close by Jason Ingold had begun disinfecting people's shoes and vehicles at his livery yard neighbouring Woolfords farm in Elstead. His horses are likely to be safe but he said local farmers would be 'absolutely gutted' if their animals were killed.

Tourism bosses were hopeful that the latest outbreak would not have the devastating effect on the industry that they suffered in 2001, when businesses nationwide were affected.