The incident was reported to the Northern Ireland Environment Agency (NIEA) on Wednesday morning and Water Quality Officers were immediately sent to the site.It has been confirmed that a significant volume of agricultural slurry escaped from a farm in the area.The environmental impact has been assessed as high.The source of the spill has been identified, but the NIEA are unable to provide details of the exact location due to its ongoing investigation.A statement from NIEA said: "Some of the slurry has reached the Ballinderry River and potentially up to six kilometers may have been affected."NIEA investigations are ongoing into the circumstances and environmental effects of the incident.Samples have been collected with a view to enforcement action once official investigations are completed.Environment Minister Mark H Durkan said: "I am concerned that such a large amount of slurry has polluted the local environment here."The important thing now is for the problem to be addressed quickly and professionally. I welcome the fact that NIEA staff have acted swiftly here and I will be keeping a close eye on developments."The Department of Culture, Arts and Leisure (DCAL) Inland Fisheries staff have been made aware of this incident.