British authorities were testing for a new outbreak of foot and mouth disease Friday, after cattle in a herd grazing several miles away from an initial cluster of cases were suspected of falling ill, raising fears the virus is spreading uncontained.

Chief Veterinary Officer Debby Reynolds said cows in a second area of the southern England county of Surrey had shown "mild clinical signs of infections," announcing that a new 1.8-mile exclusion zone had been set up around a farm previously unlinked to the outbreak.

Though the case is unconfirmed, Reynolds said the outbreak was a "developing disease situation," renewing worries of a repeat of scenes in 2001, when 7 million animals were killed and incinerated on pyres. Britain's agriculture and rural tourism industries were devastated.

The new suspected case is around 9 miles away from two farms where cases have been confirmed and a third plot where cattle have been killed as a precaution.

If the latest tests prove positive, it would suggest the initial outbreak was not contained, increasing the prospect the virus could infect herds across southern England.

"The containment and eradication of foot and mouth disease remains our priority," Reynolds said in a statement late Thursday night. "This is why we have moved swiftly to put in place a temporary control zone while we investigate this development."

Tests to determine whether the fourth farm has infected cattle are expected to take around 24 hours.

Foot and mouth disease does not typically infect humans, but its appearance among farm animals can have a swift and possibly far-reaching economic impact — several countries, including the United States, have banned imports of British livestock and Britain has voluntarily suspended exports of livestock, meat and milk products and destroyed more than 570 cows since the outbreak was spotted last week.

Britain's health and safety agency says there was a "strong probability" that outbreak originated at the Pirbright laboratory southwest of London and was spread by human movement.

The virus was first discovered last week on a farm 4 miles from the Pirbright complex, which houses vaccine-maker Merial Animal Health — the British arm of U.S.-French Merial Ltd — and Britain's Institute of Animal Health.

Merial has said it has found no evidence of breaches in biosecurity at the facility. The Institute of Animal Health said Thursday new checks of systems to prevent viruses escaping through the facility

s water system had reported no problems.

"People are going to be even more apprehensive than they have been throughout the whole of this," Hugh Broom, of the National Farmers' Union, told British Broadcasting Corp. television. "It will be worrying for members here and farmers elsewhere in the country."

On Wednesday, Britain relaxed a nationwide ban on moving livestock, believing the outbreaks had been contained to a region near the Pirbright complex.

Officials said farmers outside a surveillance zone set up around the farms where the outbreaks occurred would be able to send their animals to slaughterhouse. The first surveillance zone comprised a 6-mile radius around the initial affected farms.

Foot-and-mouth can be carried by wind and on the vehicles and clothes of people who come into contact with infected animals.