NORMANDY, England — Britain's health and safety agency said Tuesday there was a strong probability that a foot-and-mouth outbreak in southern England originated at a vaccine lab and was spread by human movement.

The outbreak was discovered on a farm just four miles from the Pirbright vaccine laboratory, which is shared by the government's Institute for Animal Health, or IAH, and a private pharmaceutical company.

There is a "real possibility" the disease was spread by human movement, and the possibility it was transmitted by air or floodwaters was "negligible," the government's Health and Safety Executive said in the report.

Environment Secretary Hilary Benn said the report brought efforts to stop the disease "a bit further forward." He said the possibility that the strain had been released by human movement would be urgently investigated, and that footpaths in the protection zone covering two infected farms would be closed immediately.

The highly contagious disease can be carried by wind and on the vehicles and clothes of people who come into contact with infected animals.

A group of cows at a second farm was confirmed to have the disease Tuesday. Cranes piled cattle carcasses onto trucks and authorities slightly expanded the protection zone around a second farm.

Both farms, about 30 miles southwest of London, were within the initial two-mile radius protection zone set up.

Britain has banned the export of livestock, meat and milk — a decision endorsed by the European Commission.