Preliminary tests on 15 birds that died at the farm showed they were infected with the H5 subtype of bird flu, Tulcea county official Lefter Chirica said.
Further tests were being conducted in Bucharest to determine if it was the deadly H5N1 strain, which has killed dozens of people around the world, Chirica said.
No quarantine has been imposed around the farm, located in Murighiol, a delta village some 250 kilometers (155 miles) northeast of the capital, Bucharest. But authorities were disinfecting vehicles in the area, as well as the shoes of those traveling through on foot.
Since 2003, it has killed at least 206 people worldwide, and it has ravaged poultry stocks in Asia, where it was first detected. Scientists believe it spread to Europe and to Africa with migratory wild birds.
In Europe in recent years, H5N1 has been found in France, Switzerland, Germany and elsewhere. In Romania, hundreds of birds died of bird flu 2005 and 2006, many in the Danube Delta, but there have been no cases of human infection in Romania.
Human cases have been recorded in Turkey and Azerbaijan, though bird flu is difficult for humans to catch. Experts fear, however, that it could mutate into a form that spreads easily among people, potentially sparking a pandemic.
Experts believe most victims were probably infected through direct contact with sick birds.