"Out of over 4,000 samples taken in the area this year, samples from 50 wild birds were found to contain genetic material of the A-H5 virus and antibodies in their blood serum," the spokesman said.
The spokesman said the presence of antibodies meant that either the birds had survived avian influenza, or remained infected but it had not spread in an open form, and could be transmitted to other birds.
He said no local bird flu cases had been registered this year. "About 6 million poultry are currently in high risk areas. Nearly 4.6 million of them have been vaccinated and over 2.3 million revaccinated," he said.