The authorities established a new three-kilometre (1.8-mile) temporary control zone on Sunday for a suspected case of foot-and-mouth disease near Petersfield, in the county of Hampshire.
It is about 45 miles away from a premises near Egham, west of London, where the disease was confirmed earlier this month.
No animals within the new control zone are being slaughtered, an environment ministry spokeswoman said. She could not give details on what kinds of animals had prompted the suspicion.
The announcement came as the Department for Environment, Food and Rural Affairs (Defra) confirmed the bluetongue virus identified in a cow in eastern England Saturday was the same strain as that found in Europe earlier this year.
The cow on a rare breeds farm near Ipswich, in the county of Suffolk, was identified as Serotype 8, a strain that had previously been found in Belgium, France, Germany, Luxembourg and The Netherlands since August 2006.
The case was not a confirmed outbreak and investigations to determine whether the disease was now circulating in Britain could take "days or weeks", Defra said. The affected premises were not under any restrictions, it added.
"It remains vitally important that farmers maintain vigilance for this disease and report any suspect cases, particularly as clinical signs may be similar to foot and mouth disease," said Britain's chief vet Debby Reynolds.
The discovery of bluetongue, which is spread through livestock by midges but is not harmful to humans, is a fresh blow to Britain's farming industry, which has had to deal with new outbreaks of foot and mouth disease since August.
Reynolds' deputy Fred Landeg told BBC television it was possible that some infected midges had been blown over from mainland Europe to eastern England and the disease could be localised to the area.
Contingency plans such as restrictions on animal movement were in place to prevent its spread if further cases are detected, he added. Work to create a vaccine is also underway but is unlikely to be available before next year.
Junior agriculture minister Lord Jeffrey Rooker said the government had been expecting bluetongue, because it had been confirmed in Europe.
"It isn't a surprise. We were expecting it," he said at the sidelines of the ruling Labour party's annual conference in Bournemouth, southern England.
Nevertheless, the president of Britain's National Farmers Union, Peter Kendall, said that while not as serious as foot and mouth, the discovery of bluetongue was still "a major concern" for them.
The affected animal, a Highland cow called Debbie, has been slaughtered as a precaution while other animals are being tested, Defra said.
The site -- Baylham House Rare Breeds Farm -- houses sheep, four breeds of cattle, pygmy goats, chickens and four types of pig, including Maori pigs from New Zealand, it said on its website.
The disease affects ruminants, including sheep, cattle, deer, camelids (camels and llamas) and goats. It causes high fevers, mouth ulcers, swollen heads and turns an infected animals' tongues blue.
The discovery of bluetongue came after another case of foot-and-mouth was confirmed late Friday in cattle in Surrey county, south-east England.
In all, there have been six cases of foot and mouth disease since the first was identified on August 3, all in Surrey, and about 1,800 animals have been slaughtered.
The first five cases have been the same strain of the disease, which last appeared in 2001 and spread rapidly across the country, ravaging the farming and tourism sectors.
The most likely cause was leaks from a nearby government-run animal disease testing laboratory and a privately run vaccine firm on the same site, public health officials have said.
The government declared Britain foot and mouth free on September 7, just days before the new cases were detected.