Romania has detected on Sunday five new suspected cases of avian flu in domestic birds in Buzau county west of the Danube delta, where the deadly virus was first isolated in October.
Romanian officials said tests on samples taken from dead poultry in a village of Padina showed presence of bird flu.
Four outbreaks have been confirmed as the highly pathogenic H5N1 strain.
Avian flu has been found in birds in more than a dozen villages in and around the Danube delta, Europe's largest wetlands, which lie on a major migratory route for wild birds.
Rapid tests indicated the H5 virus in a hen and four ducks. The officials hoped to isolate the virus and send the samples to London, as Romania has no capabilities to test for H5N1.
Authorities quarantined Padina and started to cull domestic birds in the affected household and its vicinity. Padina lies 10 km (six miles) west of the village of Ciocile, where the disease was also detected earlier this month.
On Friday, tests on an infected turkey confirmed the deadly H5N1 strain in a small village of Scarlatesti in Braila county,, west of the area where the virus was first detected in birds in the Danube delta.
The results showed the disease had spread to birds on the fringes of more populated regions of Romania. Scarlatesti, a village of 1,000 farmers in an area of lakes, is in close proximity to a number of Romanian towns, and 170 km from Bucharest.
The H5N1 strain of bird flu is endemic in poultry in parts of Asia where it has so far killed 70 people.
It remains hard for people to catch, but there are fears it could mutate into a form which passes easily from person to person, sparking a pandemic in which millions could die. There have been no cases of human infection outside of Asia.