Scientists are investigating the mysterious deaths of 16 swans on the Grand Canal, Dublin in the past 10 days.
A further 10 swans remain seriously ill after apparently contracting an infection on the water.
The sick birds are being cared for by the Dublin Society for Prevention of Cruelty to Animals.
Avian flu has been ruled out but initial reports have pointed to a form of bacterial infection such as botulism.
However, tests are continuing today at the Department of Agriculture laboratory to determine the cause of death.
The dead swans were discovered mainly between the Portobello-Suir Road Bridge section of the canal.
In addition, it was reported that there was a number of dead and rotting sea fish in the area.