There has been no confirmation so far that the government's Institute of Animal Health and a pharmaceutical company called Merial were the source of the infection. However, both laboratories have been placed within a 10km radius (6-mile) surveillance zone as a precautionary measure.
The strain of foot and mouth disease was confirmed Friday in some 60 cattle at a farm in Surrey, southwest of London. All the infected animals have been culled since then.
Defra said the incident was at an early stage and it was too soon to make any conclusions.
"All potential sources of the virus will continue to be investigated. All other precautionary measures announced yesterday remain in place," Defra said in a statement.
In the latest outbreak in 2001, more than six million cattle were slaughtered in Britain. Damage to agriculture was estimated at over 8 billion pounds (over $16.3 billion). Tony Blair, then prime minister of Britain, was strongly criticized for his handling of the situation.