Cleaning has begun at the Suffolk farm where 159,000 turkeys were culled after a bird flu outbreak.

All the empty sheds that housed the birds at the Bernard Matthews plant in Holton will be disinfected.

The Health Protection Agency (HPA) said more than 320 farm workers had taken the antiviral drug Tamiflu and so far no-one had reported being ill.

Strict controls are in place around the site near Lowestoft, but officials say the risk to humans is "negligible".

Five nations have banned imports of UK poultry following the outbreak in Suffolk. Japan, South Africa, South Korea and Hong Kong have blocked all UK poultry imports, while Russia is still allowing the importation of cooked meats.

Britain is Europe's second-largest poultry producer after France, with annual poultry exports totalling £300m.

Chief veterinary officers from the 27 EU member states discussed the outbreak at a meeting on Tuesday.

In a statement afterwards the European Commission said the UK was doing everything correctly to deal with the outbreak.

It advised against the widespread vaccination of birds at this time. An international conference on vaccination will take place in Verona in March.

A 3km (1.9 miles) protection zone and a 10km (6.2 miles) surveillance zone are in place around the farm.

Poultry owners in a wider restricted zone, covering 2,090 sq km (807 sq miles) around Holton, have been told to keep their flocks isolated from wild birds.

After the culling operation, the carcasses of the birds were transported to a plant in Cheddleton, Staffordshire, for incineration.

BBC correspondent Richard Bilton said the cleaning and disinfection of the area could last for weeks.

Experts are trying to find the source of the outbreak of the disease, identified as the "highly pathogenic" Asian strain of the H5N1 bird flu virus.

Tests could take weeks and it is possible the exact cause will never be known.