"I can assure people ... we are doing everything in our power to look at the scientific evidence and to get to the bottom of what has happened and then to eradicate this disease."
Britain has prohibited the export of livestock and livestock products in the wake of the outbreak.
A ban has been imposed on all animal movements since the virus was confirmed in cattle at a farm 53km south-west of London late on Friday night.
A three-kilometre restriction zone and 10-kilometre surveillance zone has also been placed around the farm, which lies between Guildford in Surrey and Aldershot in Hampshire.
A total of 60 cattle are to be slaughtered at the farm, the agriculture ministry said.
Christiane Hohmann, the European Commission spokeswoman, said that Britain was complying with legislation to prevent the spread of the disease.
The US and Japan placed a ban on British pigs and pork products on Saturday, adding to an existing ban on British beef in both countries because of Bovine Spongiform Encephalopathy (BSE), also known as mad-cow disease.
The US department of agriculture said that it was barring all products derived from foot and mouth-susceptible species in Britain.
Foot and mouth disease causes high fevers and blisters in cloven-hoofed animals and can often lead to death.
It can be contracted by cattle, pigs, sheep and goats, and very rarely by people.
The disease can be carried on the wheels of vehicles, in livestock units and on shoes and boots, officials said.
They said it was too soon to say how the cattle in the latest outbreak had become infected.
The 2001 outbreak started with a pig herd in northern England and spread to cows and sheep.
It eventually infected more than 2,000 farms and shut Britain out of the world's livestock export markets.