The regional authorities in Sangerhausen in the state of Saxony-Anhalt said 38 dead birds found on the shores of an artificial lake near the town of Kelbra had all tested positive.
Saxony-Anhalt is the fourth of Germany's 16 states to report cases of H5N1 bird flu since late last month, when it struck down six wild birds in the southern city of Nuremberg in Bavaria.
On Tuesday, a bird found on the other side of the lake at Kelbra in the state of Thueringen was confirmed to have had H5N1 bird flu.
Cases have also been reported near Leipzig in the neighbouring eastern state of Saxony, bordering the Czech Republic which is battling a more severe outbreak of the H5N1 avian flu.
Germany's Friedrich Loeffler Institute, the national veterinary laboratory, has suggested the disease could have jumped the border from the Czech side where it has infected turkey and chicken farms.
In Germany, the new outbreak has been restricted to swans, geese and other wild birds and has not affected poultry farms.
Germany battled a widespread bird flu epidemic in 2006. It broke out on the Baltic Sea island of Ruegen and spread to six states, including Bavaria.
The disease spread to mammals, infecting three cats and a stone marten, but did not affect humans.