The cause of the deaths of hundreds of fish in a Cwmbran lake remains a mystery, after the Environment Agency failed to find a cause.

Thousands of bream, carp and roach struggled for oxygen at Llanyravon Boating Lake last Wednesday and locals joined council staff in a bid to save them.

Torfaen council officials began pumping water into the lake in an effort to provide oxygen to the fish.

While the council put the initial death toll at over a hundred, the number could now be double that, with many more floating to the surface over the weekend.

Environment Agency officials worked at the site on Thursday and Friday, but found no pollution in the lake and failed to find a reason for the deaths.

A spokeswoman said: “Our test results show that the water quality at the time of sampling, was normal with no indication of any pollutants in the lake.”

The spokewoman said the fish died due to a lack of dissolved oxygen in the lake. “But it is not possible to determine what caused this drop in the oxygen levels,” she added.

A spokesman for Torfaen council said it is closely monitoring the lake and testing oxygen levels regularly.

He added that some dead fish sunk to the bottom and these are being removed as they float to the top of the lake.