Romania is culling thousands of farmyard birds in the Danube delta amid fears of an avian flu outbreak.
Romanian health workers are looking out for dead birds
Lab results expected on Wednesday might establish whether the H5N1 virus deadly to humans has reached Romania.
Scientists in Bucharest discovered flu antibodies in three farmyard ducks found dead in a remote village late last month, Romanian officials said.
Flu vaccinations are being carried out in Tulcea County in the delta, where controls now affect seven villages.
Ceamurlia de Jos, where the duck cases were found, is under quarantine.
Although bird flu antibodies were found, the presence of flu itself has not yet been confirmed. Romanian officials say it may take two weeks before the type of virus is identified.
But about 45,000 domestic birds will have to be culled in the region, where poultry is a staple food, Romanian officials say.
In neighbouring Bulgaria experts are testing samples from three dead birds found in different areas of the Pleven region, about 100km (60 miles) from Bulgaria's Danube river border with Romania.
Turkey is racing to contain a suspected bird flu outbreak at a turkey farm in the western town of Kiziksa.
Romania and Turkey are anxiously awaiting the results of tests to find out whether they have been hit by the H5N1 strain, which has killed more than 60 people in South-East Asia over the past two years.
There is no evidence so far of the strain being passed between humans.
Analysts say the Danube delta is particularly vulnerable because it lies along a route taken by migratory birds, which often mix with domestic ducks and geese.
The Balkan neighbours of Romania and Turkey have banned imports of poultry from the two countries, as have Ukraine and Switzerland.
UN officials said on Tuesday they were working to boost production of a vaccine to protect populations in case bird flu mutates and sparks a human influenza pandemic.
Romania's agriculture ministry has promised 10bn lei (£192,000; $335,165) in compensation to villagers angered by the cull, the BBC's Delia Radu reports from Bucharest.
The offer amounts to 60-80,000 lei (£1-£1.50; $2-$2.7) per kilogram of lost poultry.
But Ceamurlia's mayor Mihai Carciumaru told the BBC that 7bn lei was needed for Ceamurlia alone.
Bucharest has also offered the affected villagers food aid, but they insisted on compensation graded according to the value of the birds culled.
Romania has now banned hunting in the delta.