Carcasses of six dead birds found in two counties are being tested following the confirmation of a case of the virulent strain of bird flu in Scotland.
Remains of five birds were discovered at the River Bann near Portglenone, Co Antrim, and other remains were found in a field near Moira, Co Down.
The bodies of the birds, understood to be swans, have been taken for a preliminary investigation by scientists at the non-governmental Agriculture Biosciences Institute laboratory at Newforge in south Belfast.
Results expected today will establish if further, more detailed, tests are required to confirm Ireland's first case of bird flu.
Britain's first case of the highly contagious H5N1 strain of bird flu was announced yesterday. The departments of agriculture in both the North and the Republic said yesterday that contingency plans were ready should bird flu be confirmed.
Chief veterinary officer at the department of agriculture and rural development (Dard) Bert Houston said: "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."
The North's agriculture minister Lord Jeff Rooker, referring to the finding of the highly contagious H5N1 strain in Fife, Scotland, said: "We have decided that it is not necessary to require the housing of birds in Northern Ireland at this time."
He added: "I must stress that avian flu is a disease of birds which does not pass easily to humans. Advice from the department of health is that the risk to human health is extremely low. On the basis of current scientific advice, the Food Standards Agency advises that avian flu does not pose a food safety risk for consumers."
A department source at Stormont was unable to say how long the birds discovered yesterday had been dead.
The Irish Times was told the remains could have been interfered with by dogs or wild animals and this had first to be ruled out.
Dard has been routinely testing the carcases of dead birds found in Northern Ireland since last autumn, following heightened awareness of the westward spread of bird flu. More than 200 tests have been carried out but none has been positive.
SDLP Assembly member for North Antrim Sean Farren called for a calm response from the public. "Local people will be concerned by the news that a number of dead swans have been discovered . . . However, I must remind people that these deaths may not have been caused by the bird flu virus and people must remain calm but sensible," he said.
"If anyone notices anything unusual in the area relating to other birds then they should contact the relevant authorities immediately. I sincerely hope that these swans have not died from the bird flu virus."