A fish kill in a number of rivers in County Tyrone is being investigated.
It is believed thousands of fish have so far been killed as a result of pollution which was first discovered on Aghlisk river in Fintona on Monday.
The pollution continued on downstream into the Owenreagh River and has now reached Drumragh River at Ballynahatty where fish are continuing to die.
The Northern Ireland Loughs Agency is investigating and samples of the rivers have been taken.
Aeration equipment has been used to re-oxygenate the water.
"The agency are continually working since the report came in and the investigation is ongoing," its director of conservation John McCartney said.