Earlier this month, Romania became the first European mainland country to detect H5N1 in birds in two villages in the Danube delta, in the southeast of the country.
Last week, a heron was diagnosed with anti-bodies for bird flu in the eastern county of Vaslui, 100 km (60 miles) north of the Danube delta, in an area not in the immediate vicinity of a any villages or towns.
"Yesterday, the laboratory in Britain confirmed the presence of the H5N1 virus in the heron found in Vaslui county, diagnosed with bird flu on October 21," the ministry said in a statement.
Authorities in Vaslui county told people to keep chickens indoors to avoid the virus spreading to domestic birds.
The ministry said more than 500 tests were conducted in the past two weeks on birds in the southeast of the country and all were negative for bird flu.
The deadly strain was first found in samples taken from two villages in the Danube delta, 40 km (25 miles) apart. More than 21,000 domestic birds in the two villages were killed and the villages were placed under quarantine.