UPDATED 6.22PM | Selangor water authorities have identified the cause of the water pollution in Sungai Selangor, which caused water supply disruption in the Klang Valley since early morning today.

According to Air Selangor, its investigation revealed that the pollution came from a land plot in Mukim Sungai Tinggi, Hulu Selangor, which houses 57 aquaculture ponds for catfish breeding.

"The odour pollution is believed to have started when water was discharged from one of the fishponds, with the purpose of emptying it.

"Based on the investigation, the premises have made discharges through two outlets, which flowed in high volume into a trench that leads to Sungai Selangor and caused the pollution," it said in a statement.

Following this, Air Selangor had issued an order to the operator of the premises to stop the discharges and conduct immediate remedial works.

The authority has also launched an investigation under Section 79 of the Selangor Water Management Authority (Luas) Act for pollution of water sources, which carries a penalty of a fine of between RM200,000 and RM1 million, and a jail sentence of not more than three years, if found guilty.

Earlier today, Air Selangor reported a temporary water supply disruption after the Sungai Selangor Phase 1, Phase 2, Phase 3 and Rantau Panjang water treatment plants (WTP) were shut down due to pollution.

"Following the termination of the four WTPs, a total of 861 areas in Kuala Lumpur, Petaling, Klang/Shah Alam, Gombak, Kuala Selangor, Hulu Selangor and Kuala Langat experienced water supply disruptions.

"Air Selangor found the water supply distribution to be in an unstable state where most water tanks in residential areas experienced a sharp decline.

"Affected users are expected to receive water supply starting at 3pm today, in stages, with a full recovery at 11.59pm tomorrow," said Air Selangor in a statement.

886,297 accounts affected by the supply disruption

It said the shutdown of the WTPs caused an unscheduled water supply disruption involving 886,297 accounts.

The Rantau Panjang WTP was shut down temporarily at 11.30pm last night (Dec 7) and the other three stations were shut down at 1am this morning. However normal services resumed within four hours.

"Air Selangor would like to inform that the Rantau Panjang Water Treatment Plant has been operating since 3.30am this morning and Sungai Selangor Water Treatment Plants 1, 2 and 3 resumed operating at 5am, after the pollution in Sungai Selangor recorded readings at level 0 TON (Threshold Odour Number) three times.

"Air Selangor will provide water supply assistance by sending water tankers to the affected areas, with priority given to critical premises such as hospitals and dialysis centres," the statement read.

Air Selangor said it understood the situation of consumers who needed clean water, especially during the conditional movement control order, and was making all efforts to minimise the impact on the affected users.