British authorities have ordered the slaughter of a second herd of cattle suspected of being infected with foot-and-mouth disease.

Britain's chief veterinary officer Debby Reynolds said veterinarians on Monday night began killing some 50 cattle at the second site, located south of London near the farm where the first group of infected cattle was found.

Animal health specialists are trying to pinpoint the source of the outbreak, focusing on a research center near the site of the first outbreak. But officials at the center say there have been no security breaches.

Investigators are looking into possibilities the highly infectious virus may have spread, including the fact that recent floods may have helped transmission.

Foot-and-mouth disease affects animals with cloven hooves, but it is not considered a threat to humans.

On Monday, the European Union confirmed a formal ban on British live cattle, pigs, sheep and goats, as well as meat and milk products.

South Korea imposed a ban on British pork and pigs, while Russia banned the import of pork from Britain.

Britain itself has banned the transport of all cattle, pigs and sheep within the country.

A British epidemic in 2001 devastated rural English communities and cost more than $16 billion to bring under control.

Some information for this report provided by AP, Reuters and AFP.