Northern Ireland Water has been fined £2,000 after untreated sewage polluted a river in Co Antrim.
A blockage was caused by inappropriate items being put into the sewerage system, resulting in a discharge from a pumping station stretching 500 metres into the Six Mile Water.
The problem at Clotworthy Bridge, Antrim, was discovered last May and NIW staff said material which should not have been placed into the sewers caused one of the pumps at Masserene sewage pumping station to trip.
The fine was imposed at Antrim Magistrates' Court.
A Northern Ireland Environment Agency spokesman said: "A sample taken at the time of the incident confirmed that the discharge contained poisonous, noxious or polluting matter which was potentially harmful to fish life in the receiving waterway."
A NIW spokesman said everyone in Northern Ireland could help reduce pollution incidents.
"The advice is simple, only toilet roll and human waste should be flushed down the toilet, for everything else - bag it and bin it, don't flush it," he said.
"A thorough investigation by NI Water has also highlighted areas we can improve upon to respond as quickly as possible to future incidents, thereby minimising the environmental impact of such discharges."
NIW said it was working to reduce these occurrences by investing in water and wastewater services to bring them up to an acceptable standard, adding a new replacement sewage pumping station due to became operational in September 2010.
The spokesman said: "With completion of investment programmes such as this, NI Water is confident that pollution incidents will become less common."