More than 1,000 fish have found dead following a pollution incident along the River Callan in Co Armagh.
The Northern Ireland Environment Agency (NIEA) is continuing to examine the area.
So far, around 1,000 brown trout and 100 salmon have been killed.
The agency has confirmed that ‘a definite line of inquiry is now being followed.’
Samples have been collected to support potential legal action.
