PETALING JAYA (THE STAR/ASIA NEWS NETWORK) - Hundreds of thousands of people in four districts in the Klang Valley were on Sunday (Oct 4) affected by water-supply cuts due to a river-pollution incident, barely a month after the previous incident raised widespread public anger.

A total of 309,687 consumer accounts from the Petaling, Hulu Langat, Kuala Langat and Sepang districts were affected on Sunday after two water-treatment plants were shut down due to the detection of pollution in Sungai Semenyih, the raw water source for the plants.

The Klang Valley refers to Malaysia's most densely populated districts that include the federal territories of Kuala Lumpur and Putrajaya, and districts in southern Selangor.

In a statement on Monday morning (Oct 5), utility provider Pengurusan Air Selangor Sdn Bhd said the Sungai Semenyih and Bukit Tampoi water treatment plants were still not fully operational.

"As of 7.30am, pollution is still detected at Sungai Semenyih and is at the level of 7 tonne (threshold odour number) at the Bukit Tampoi water treatment plant and 5 tonne at the Sungai Semenyih water treatment plant respectively," Air Selangor said in the statement as quoted by the Malay Mail newspaper.

State authorities have traced the source of the odour pollution to an Industrial Zone and a goose and duck farm sitting on the banks of Sungai Batang Benar and Sungai Pajam in Negeri Sembilan, Selangor's neighbouring state.

"Both of these suspected sources of pollution are situated in Negri Sembilan. We could not detect any sources from within Selangor. From the farm, until 9am yesterday, there was a big cleaning up at the coops which washed out to the rivers," the Selangor Environment, Green Technology and Consumer Affairs Committee chairman Hee Loy Sian said at a press conference on Monday.

"We have yet to pinpoint exactly but these are the suspected places," he added.

Hee also said that the Sungai Semenyih and Bukit Tampoi water treatment plants would only resume operations after the odour had been removed.

He said that action will be taken against the perpetrators once the source has been identified.

Meanwhile, Selangor Environment, Health, Cooperatives and Consumerism Committee chairman S. Veerapan said authorities were also investigating if leachate - the liquid that drains or 'leaches' from a landfill - could have been responsible for this.

Public anger boiled over last month when water supply was cut to more than 1.2 million consumer accounts in the Klang Valley.

The shutdown of four treatment plants from Sept 3 was caused by chemical effluents that were discharged into a drain at a vehicle maintenance plant in Rawang that flowed into a river which supplies raw water to the treatment plants.

Supply was progressively restored between Sept 6 and 8.

The factory, which had been operating for years without permits, has been closed.

Five people - four brothers who are directors of the maintenance plant, as well as a workshop manager - were charged with polluting Sungai Gong in Rawang district, causing the disruption of water supply.

The offences were allegedly committed at the premises of Yip Chee Seng & Sons between Sept 2 and 3.

If convicted under a section of the Penal Code, the men could face a jail sentence of between five and 30 years, or a fine, or both.

If convicted under the Environmental Act, they face a fine not exceeding RM100,000 (S$32,900), or a jail sentence not exceeding five years, or both.