Britain's farming industry was in crisis last night after the Government banned all exports of live animals, meat and dairy products following the nation's first outbreak of foot-and-mouth disease for 20 years.

The ban came as it was revealed one of the infected animals at the centre of the outbreak came from a market in Selby, North Yorkshire.

Five farms were ringed by five-mile animal movement exclusion areas last night as attempts to restrict the disease to a single Essex abattoir were stepped up.

The Government said a total of 300 pigs and 60 cattle had been killed at the slaughter house - Cheale Meats in Little Warley, south of Brentwood - and an adjacent farm owned by the same family.

A veterinary inspector first discovered the outbreak on Monday after 27 infected pigs were found at the Essex abattoir.

The abattoir and two farms from which the animals were delivered last Friday - one in Great Horwood, Buckinghamshire, and the other in Freshwater Bay on the Isle of Wight - were immediately placed under five-mile exclusion orders banning the transport in and out of the restricted areas.

A farm near Goole, East Yorkshire, was later placed under restrictions after one of the infected pigs involved was discovered to have been delivered to the Essex slaughter house from Selby market.

Restrictions were also placed around a farm near Stroud, Gloucestershire, following a suspected outbreak of foot-and-mouth.

A Ministry of Agriculture, Fisheries and Food (Maff) spokesman said the Yorkshire farm was a possible source of the outbreak, although it was "very unlikely".

Last night, the Food Standards Agency said the disease posed no threat to food safety.

Rob Simpson, of the National Farmers' Union, North-East and Yorkshire, said: "With the industry beleaguered already, this is the last thing we need.

"Any restrictions will place a huge burden on the industry, but we recognise the importance of containing this outbreak."

The European Commission last night imposed its own export ban on British livestock, and animal products.

Maff Chief veterinary officer Jim Scudamore said investigators were working tirelessly to identify where the disease started.

Although foot-and-mouth can be passed from farm to farm through the air, they were looking at the more likely possibility that animals had caught the disease from one of the transporters used to make deliveries to the Essex abattoir.

Farmers are urged to report any suspected symptons of foot-and-mouth disease, including high temperatures, a lack of milk production in cattle, lameness and a loss of appetite.

The incubation period was three to 14 days, although the particular strain of virus identified seemed to be a lot faster.

Agriculture Minister Nick Brown said: "We are faced with what is potentially a very serious situation.

"The way forward is that we have to get on top of the situation to bear down on the source and check every single movement in and out of the area where this has been identified and to slaughter the infected animals."

Mr Brown said farmers who had to slaughter livestock affected by the disease would be compensated at the full market value. He was unable to predict how long the ban on exports might be in place.

The Meat and Livestock Commission calculated that the export ban would cost the industry £8m a week in lost revenue. Lost dairy product sales would add to this figure.

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