The pollution of Sungai Selangor which caused several water treatment plants to cease operation was due to the dumping of industrial wastes into the river.

Selangor Menteri Besar Mohamed Azmin Ali said however, the Selangor Water Management Authority (Luas) and the Selangor Department of Environment (JAS) were still investigating the actual cause of the incident.

"The pollution of the river was due to spillage of hydrocarbon which affected supply of clean water to almost 60 percent of the consumers in the state, involving nearly 800,000 customer accounts.

"The state government regrets the pollution recurred after a diesel pollution incident at Sungai Gong in August last year whereby, the state government seized the land and took legal action against the culprits," he said.

Speaking at a media conference after chairing an emergency meeting on the incident at the State Secretariat Building here Sunday evening, he said the situation was expected to be fully restored in three days.

At the same time, Mohamed Azmin said the state government had directed Syarikat Bekalan Air Selangor Sdn Bhd (Syabas) to raise production and distribution of water immediately, including stationing static tanks at several affected areas and update the company's website, as well as expanding manpower at its customer service centre, Puspel.

"The National Water Services Commission (Span) will assist by obtaining additional lorry tankers from nearby states and the Armed Forces.

"The operator of SSP1 (Sungai Selangor Phase 1), Splash (Syarikat Pengeluar Air Sungai Selangor Sdn Bhd) has been told to raise production from 950 million litres to 1,045,000 litres daily, with immediate effect as a mitigation measure, he added.

He said the priority of the emergency water supply assistance would be given to critical consumers such as hospitals, dialysis centres and welfare homes, as well as for urgent situations such as weddings or funerals.

Commenting further on the incident, Mohamed Azmin said the operators of several water treatment plants stopped operation at 8pm Saturday to prevent polluted substances from entering the treatment system which resulted in the disruption of water supply.

He said all water treatment plant operators involved had started pumping raw water at 5am Sunday.

"Syabas said water supply in several affected areas will be restored from 8am Monday. Nonetheless, certain locations, especially those on higher ground and at the end of the distribution system such as Pulau Indah, Port Klang and Banting will be restored in stages," he added.

Mohamed Azmin declined to comment when asked if the incident involved elements of sabotage but stressed the party responsible would not escape action, including seizure of land.

He stressed that the pollution incident would not involve water rationing in the state.