The authority said the river was found to be brightly coloured during a routine patrol around 6.40pm. It was due to effluent released by a factory in Beranang.

“Checks by Luas on the premises in question found the coloured effluent at its final discharge point, which streams into Sungai Kabul and into Sungai Beranang and Sungai Semenyih.

“Luas has ordered the premises to halt operations and close off its discharge immediately,” it said on Facebook yesterday.

The authority said it had issued the premises an order under the Luas Enactment 1999 to immediately conduct cleaning work at the river and other affected areas.

“Luas has also taken samples at the affected locations for analysis by the chemistry department for further enforcement action,” it said.

Luas said it was conducting checks at Sungai Kabul every 30 minutes and was also monitoring the factory’s cleaning work.

It said it activated its yellow alert for the purposes of thorough investigation and prevention, as the effluent could potentially affect the Sungai Semenyih water treatment plant.