A swan that flew into Croatia from neighboring Hungary was found carrying the deadly H5N1 strain of bird flu, said reports reaching here from Zagreb on Wednesday.

"The swan, which had a ring 10JJ showing that it had been tagged in Hungary, is positive for bird flu. It is the highly pathogenic H5N1 virus," the reports said, citing a statement released by the Croatian agriculture ministry.

Croatian experts informed Hungarian authorities about their test findings, reports said.

The swan was shot dead on Oct. 25 in the village of Zdenci in eastern Croatia, where health authorities have detected two groups of dead swans positive for the deadly H5N1 strain since Oct. 21.

Croatian authorities believe the two groups of eight infected swans belonged to the same flock, which came from Hungary.

Hungary authorities said last week that the swan was healthy when it was ringed at Hungary's Lake Balaton, some 300 kilometers north of Zdenci. Hungary has so far reported no cases of bird flu.

But Croatian ornithologists believed the swans were already infected when they arrived in the former Yugoslav republic.

The deadly form of the virus was recently confirmed in nearby Romania and Turkey, having been spread by migratory birds from Asia via Russia. A separate case was found in a parrot in quarantine in Britain. The strain has been closely watched by experts who fear it could mutate into a form easily transmitted to people and cause pandemic.