Three northern German states placed poultry in quarantine on Thursday to prevent it coming into contact with migrating birds carrying the avian flu virus from eastern Europe. In Lower Saxony in the north of the country, Germany's biggest poultry-rearing state, chicken, geese, turkey and ducks will be shut inside until the end of November on most farms, state authorities said. Around 10 percent of Lower Saxony's annual chicken production of 72 million birds are normally kept outdoors. Similar measures went into operation in Mecklenburg-Western Pommerania and North Rhine-Westphalia. Some experts however said the measures were excessive. "Only healthy birds migrate," said Ortrud Werner of the German national laboratory for avian flu. "The biggest danger for Germany stems from the illegal importing of infected or sick birds," she said. Russia and Kazakhstan have been hit by an epidemic of avian flu, which can be transmitted to humans. It is the same strain which killed several dozen people in Asia.