Britain's health and safety agency said Tuesday that there is strong probability that a foot-and-mouth outbreak in southern England originated at a vaccine lab.

There is a "real possibility" the disease was spread by human movement, and the possibility it was transmitted by air or flood water was "negligible," the Health and Safety Executive report said.

Earlier Tuesday, tests confirmed a second outbreak in a herd within the initial 2-mile-radius protection zone set up around the farm where a first group of infected cattle was found.

The outbreak, 30 milessouthwest of London, occurred just 4 miles from a laboratory that produces vaccines containing the same rarely seen strain of foot-and-mouth disease.

News of a second confirmed outbreak fed fears of a repeat of scenes in 2001, when 7 million animals were culled and incinerated on pyres, devastating agriculture and rural tourism in Britain.

"We were starting to think this virus had been contained and maybe we were going to be getting back to normality in a few weeks," farmer Laurence Matthews, who owns the farm where the second infected herd grazed, told British Broadcasting Corp. radio Tuesday.

"Now this has set us back again and most farmers, and I've been speaking to a few, are very, very scared," he said. Matthews, who met Prime Minister Gordon Brown when the leader toured the region Monday, said the infected cows belonged to a fellow farmer who used his land.

Matthews called for local footpaths to be closed within the exclusion zone, saying some farmers believed the virus could be carried and spread on the feet of walkers passing through the area.

The outbreaks come on the heels of widespread flooding, and investigators were investigating the possibility that the flooding might have helped spread the virus.

Britain's Chief Veterinary Officer Debby Reynolds said Monday that the strain found in the first herd matched samples taken during Britain's 1967 outbreak of foot-and-mouth disease. The strain had not been seen in animals for a long time — but was used to produce vaccines, she said.

The vaccine laboratory is shared by the government's Institute for Animal Health, or IAH, and a private pharmaceutical company, Merial Animal Health, the British arm of Duluth, Georgia-based Merial Ltd.

Merial said it found no evidence of a breach in biosecurity, and the IAH claimed a check of records found "limited use" of the virus in the past four weeks.

Foot-and-mouth disease affects cloven-hoofed animals, including cows, sheep, pigs and goats, but does not typically affect humans.

The prime minister, who broke off a vacation to handle a response to the outbreak, said investigators were trying to pinpoint the cause of the outbreak — but acknowledged that the disease strain found in the first infected herd was the same used at the research laboratory.

National Farmers' Union president Peter Kendall said the latest case was "not entirely unexpected," given the nature of the disease.

The first herd of around 120 cows from a farm in Normandy, outside Guildford, was slaughtered Saturday after the virus was identified and confirmed in two animals, the Department for the Environment, Food and Rural Affairs said.

A farmer first noticed signs of illness in his cows on July 29 and notified authorities on Thursday, according to a government report filed to the World Organization for Animal Health.

Britain has banned the export of livestock, meat and milk — a decision endorsed by the European Commission. The commission also backed London's decision to halt the movement of cattle, sheep, goats and pigs nationwide to prevent the spread of the virus.

Imports of British pigs and pork products have been banned by the United States, Japan, Russia and South Korea in response to the outbreak. The United States and Japan already have bans in place on British beef imports.