(Adds details, background) AMSTERDAM, March 5 (Reuters) - The Dutch Agriculture Ministry on Monday ordered commercial poultry to be kept indoors from March 7 to prevent a possible bird flu spread during the migration season this spring. Veterinary experts believe that migratory birds represent a serious risk in the spread of the deadly H5N1 avian flu virus, the ministry said in a statement. The Netherlands, Europe's second-biggest poultry producer after France, temporarily ordered its poultry indoors last month after H5N1 was found in a turkey farm in Britain, rekindling fears the disease could return to northern Europe. A UK report had said an earlier outbreak in Hungary was the most plausible source, a theory which the eastern European country rejects. The Netherlands, a top world poultry exporter, has never reported H5N1 in commercial poultry but it was hit by H7N7 avian flu in 2003, which led to the culling of 30 million birds, about a third of the poultry flock, as well as one human death.
