More than 1,000 fish have been killed in a pollution scare in Tyrone.
Trout, sticklebacks and roach are among the dead species found in the Oona River near Dungannon.
Investigators have blamed an “agricultural source” for the kill, which is classed “high severity”.
The Northern Ireland Environment Agency (NIEA) and the Inland Fisheries agencies are investigating the pollution. Environment Minister Mark H Durkan said: “I am concerned about this and I am keeping a close eye on the situation along with NIEA officials.”
Samples have been taken from the river for analysis.
An NIEA spokeswoman said: “Investigations are ongoing and the (fish kill) count is continuing.”
She added: “The water quality impact of this water pollution incident is being classified as high severity.
“Investigating officers have identified a potential source of the discharge and statutory samples have been taken by NIEA.”
The River Oona is part of the Blackwater river system.