LONDON -- Livestock on an English farm that were tested after showing signs of possible foot-and-mouth disease do not have it, Britain's chief veterinarian said Saturday. The result strengthens indications that the highly contagious livestock ailment has not spread beyond the small area where it was first discovered last week.
"The latest tests on the farm to the east of the surveillance zone are negative," Chief Veterinary Officer Debby Reynolds said.
Reynolds announced late Thursday that cows in a second area of the southern England county of Surrey had shown "mild clinical signs of infections" and were being tested. Officials established an exclusion zone around a farm previously unlinked to the outbreak and some 10 miles from the two confirmed cases of the disease.
The Department for Environment, Food and Rural Affairs on Saturday lifted restrictions around the farm, near the village of Wotton.
British authorities are increasingly confident that they have prevented foot-and-mouth from spreading to livestock across the country, a development that could have devastated the rural economy. An epidemic in 2001 led to the slaughter of 7 million animals and shut British meat out of world markets for months.
Prime Minister Gordon Brown said Friday that officials had "restricted the disease to a limited area of this country."
"The risk of it spreading out of these areas is low, if not negligible," he said.
An interim epidemiology report on the outbreak has concluded that the disease probably spread by human movement from a research laboratory facility in Pirbright, about 30 miles southwest of London.
The complex houses vaccine-maker Merial Animal Health -- the British arm of U.S.-French pharmaceutical firm Merial Ltd. -- and the government's Institute of Animal Health.
Experts are still trying to determine exactly how the disease spread. Foot-and-mouth can be carried by wind and on the vehicles and clothes of people who come into contact with infected animals.
Animals on two farms near the lab complex tested positive for foot-and-mouth and were slaughtered. In all, about 500 animals have been killed on the two infected farms and -- as a precaution -- on three nearby properties.
Foot-and-mouth disease affects cloven-hoofed animals including cows, sheep, pigs and goats. It does not typically infect humans, but its appearance among farm animals can have a far-reaching economic impact. Several countries have banned imports of British livestock and Britain has voluntarily suspended exports of livestock, meat and milk products since the outbreak was identified Aug. 3.
Reynolds said farmers should remain vigilant for signs of disease.
"It is Day 8, very early in foot and mouth disease 2007, so relentless vigilance amongst the farming community is the order of the day," Reynolds told the British Broadcasting Corp.