OFFICERS from Natural Resources Wales are probing an oil spill on the rivers Tarrell and Usk in Monmouthshire.
150 litres of diesel has been spilled which has affected a 2km section of the river. Early indications have shown that insects have been killed, but no fish.
The source of the pollution has been stopped, but officers are investigating how the spill happened.
A spokesman for Natural Resources Wales said local anglers reported the incident. He added they will be monitoring the river closely over the coming days and will take further action if necessary.
If anyone has information about the spill they are asked to contact Natural Resources Wales' 24-hour pollution reporting line – 0800 80 70 60.