DOG walkers and lovers of the outdoors were left shocked when they came across a South Wales river running orange over the weekend.

Extraordinary photos show parts of the river Afon Llwyd running “rust orange”.

The Afon Llywd, which can reach as far north as Blaenavon, runs past the likes of Pontypool, Cwmbran and Caerleon before hitting the river Usk.

Extraordinary photos taken from places including New Inn show the river’s rust-orange colour.

South Wales Argus: Extraordinary photos taken from places including New Inn show the river’s rust-orange colourExtraordinary photos taken from places including New Inn show the river’s rust-orange colour (Image: Lauren IIes)

South Wales Argus: Torfaen Council were made aware of the rare occurrence on January 12Torfaen Council were made aware of the rare occurrence on January 12 (Image: Torfaen Council/ NRW)

South Wales Argus: NRW took water samples over the weekendNRW took water samples over the weekend (Image: Torfaen Council/ NRW)

Torfaen Borough County Council were made aware of the rare occurrence as was Natural Resources Wales on January 12.

The council said: “NRW officers attended the site yesterday evening (January 12) to investigate and have returned this morning to continue the investigation in daylight hours. 

“NRW suspect that pollution has been caused by a mine water breakout into the Cwmsychan Brook in the area of the British, near Abersychan, which has impacted also the Afon Lwyd.”

Now, NRW has confirmed the source of the strange colour.

In a post put on X, formally Twitter, today, January 14, Wales’ environment regulation agency said the source of the strange colour was a former ironworks near Abersychan.

South Wales Argus: Photos of the river today, January 14Photos of the river today, January 14 (Image: Torfaen Council/ NRW)

South Wales Argus: The source was mine water pollution at the Cwmsychan Brook Culvert, a former iron works site near AbersychanThe source was mine water pollution at the Cwmsychan Brook Culvert, a former iron works site near Abersychan (Image: Torfaen Council/ NRW)

A spokesperson for NRW said: “By working closely with the Coal Authority we have confirmed the source of mine water pollution as the Cwmsychan Brook Culvert, a former iron works site near Abersychan in Torfaen.

“It now appears to have subsided, and the river is much clearer today though orange sediment remains on the riverbed.”