The ban on the movement of poultry, eggs and bird manure brought in to halt the spread of bird flu has been broken at least twice, according to the Dutch food safety body NVWA.

The police stopped two lorries on Monday and found they were transporting the waste matter from a poultry slaughterhouse. One lorry was in the north-east of the country, the other in Noord-Holland province. In both cases, fines were issued and the contents of the lorry destroyed, the NVWA said.

The ban on the movement of poultry was brought in on Sunday following the discovery of avian flu at a factory farm in Hekendorp, south of Utrecht.

Closed

The 150,000 battery chickens at the farm are being destroyed and the farm will remain closed for at least a month. It is expected that all the chickens will be gone by the end of Tuesday.

The six buildings in which they were housed will then be cleaned and disinfected and closed off for two weeks. They will then be checked to see if the virus has gone. If that is the case, they will be closed off for a further two weeks and then be checked again.

The chance that the outbreak of bird flu was caused by migrating birds is small, according to the Dutch institute for ecology NIOO, despite claims by experts on Monday.

Recent research shows that migrating wild ducks are unlikely to bring bird flu with them. However, the NIOO is still looking into other migratory birds such as geese.