Scientists analysing the virus responsible for the Surrey foot-and-mouth disease outbreak have revealed it may have come from their own site.

The Department for the Environment, Food and Rural Affairs (Defra) this evening issued a statement saying the strain is used at the Pirbright laboratory of the Institute of Animal Health (IAH) and a pharmaceutical company Merial Animal Health Ltd, which shares the site. Pirbright lies about five kilometres (three miles) to the North of the farm where the outbreak occurred.

The type of virus is similar to one used in vaccinations and is not one known to have been found recently in animals. It was last seen among the animal population during the 1967 outbreak of the disease.

At 10pm tonight, Defra imposed a new, larger protection zone around both the farm and the Pirbright facility. The 10km-wide surveillance zone has also been widened.

Defra said: “This strain is present at the IAH and was used in a batch manufactured in July 2007 by the Merial facility. On a precautionary basis Merial has agreed to voluntarily halt vaccine production.

“Immediate action is being taken with an investigation led by the Health and Safety Executive at the Institute for Animal Health and Merial.

“In addition an urgent independent review into biosecurity arrangements at both sites has been commissioned led by Professor Brian Spratt of Imperial University.  It will report to Hilary Benn and Debby Reynolds.

“It is too soon to reach any firm conclusions. All potential sources of the virus will continue to be investigated. All other precautionary measures announced yesterday remain in place.”

If it is confirmed that the Pirbright site is the source of the outbreak, it is hoped that the rapid imposition of animal-movement restrictions will confine the disease to the area of Surrey at the centre of the current crisis.

In Scotland, Rural Affairs Secretary Richard Lochhead declared the countryside ‘open for business’. Agricultural shows at Dumfries and Turriff went ahead without livestock. At Perth Show, cattle already on the showground had to be isolated midway through the two-day event after the initial declaration by Defra. Mr Lochhead, along with Scottish First Minister Alex Salmond, will attend Turriff Show tomorrow.

In Wales, the Gower Show was cancelled and the Brecon Show was staged without cattle and sheep.

Welsh Deputy First Minister Ieuan Wyn Jones stressed the principality’s countryside was still open: “There are no plans for a blanket closure of footpaths and rural Wales is there for people to enjoy.”

In Northern Ireland, disinfectant mats have been placed at airports and ports. No animal-movement restrictions are in force, but imports of livestock from Britain have been prohibited. The Stormont government is also liaising with the Dublin administration to help prevent the disease coming into the island of Ireland.