A number of dead swans discovered by a river in County Antrim are being examined by government vets.
The dead swans were taken away for further tests
The remains were found on the River Bann near Portglenone.
Police have cordoned off the area amid concern about bird flu, but the Department of Agriculture said the operation was routine.
Council workers found a newly-dead swan on Thursday. Later, a second partly decomposed bird and two badly decomposed swans were found nearby.
Meanwhile, officials have also recovered the carcass of a dead swan from a grassy field near Moira.
Northern Ireland's chief veterinary officer, Bert Houston, said tests were being carried out on the dead swans.
He said 12 other dead birds have already been tested and no trace of the H5N1 virus has been found.
"All of those tests have been negative," he said.
Mr Houston added: "We have good contingency plans in place and have implemented all the EU requirements.
"I am confident that if avian influenza did come to Northern Ireland we would be able to handle it."
Health experts have been carrying out tests on a swan found dead in Scotland that tested positive for bird flu.
The EU's bird flu laboratory in Surrey has now confirmed that the UK has its first case in a wild bird of the H5N1 strain.