Bulgaria's state veterinary service has sent inspectors to border areas with Romania, to make sure instructions against bird flu are strictly followed.
The country has not registered any cases of the disease yet, but is widely seen as the next potential destination of the outbreak, after neighbours Romania and Turkey found contaminated ducks.
Bulgarian health inspectors have been sent to Rousse, Silistra and Dobrich, situated along the Danuber River and near the area where Romania's avian flu outbreak occurred.
Supervisors are also headed to the Black Sea ports of Varna and Burgas, the state Bulgarian National Radio said Sunday.
Meanwhile, Romania has sent samples for examination in London. Tests should discover whether it was the H5N1 strain which has killed 65 people and millions of birds in Asia since 2003 and been registered in Russia and Kazakhstan.
Experts fear H5N1 could mutate into a disease that spreads easily among humans, sparking a pandemic that could kill millions, Israeli Haaretz says.