NATURAL Resources Wales (NRW) confirmed it has dealt with a pollution incident in Pontithel.
Officers from NRW found around 200 dead bullhead fish in a seven-metre stretch of the Llynfi River.
They have now launched an investigation to find out what caused the pollution.
A spokesman posted on the NRW Twitter page: “The pollution has stopped and no further fish deaths have been seen.
“Our officers are gathering evidence and taking water samples. The investigation is still ongoing.”
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