Thousands of fish have been killed by pollutants along a 12-mile stretch of a river in County Antrim.
Anglers are warning that fish stocks in the Ballymartin River and Six Mile Water may never recover.
Paul Erwin from the Antrim and District Angling Association said fish were lying dead in both rivers. He said the same area had been polluted in 2006.
There is also concern that the impact of the pollutants could spread to birds and otters in the area.
The Environment and Heritage Service's Water Quality Service is investigating the incident.
Mr Erwin said his association had just completed major enhancement works at the end of last year.
"The resulting increased productivity will have been negated as all spawning beds and food supplies over this stretch of waterway will have been poisoned," he said.