KUALA LUMPUR - Malaysian authorities on Saturday (Sept 5) remanded for six days four factory managers who are suspected of involvement in a water pollution case that caused water supply to be cut to millions of people in Selangor and Kuala Lumpur.

The Selangor chief minister said that the factory in Rawang district will be demolished as it doesn't have planning permission to be built.

Media reports say the vehicle-maintenance factory allegedly poured used industrial oil into drains that flowed into Sungai Gong, one of the rivers where its water is treated and later piped to homes, industries and offices.

Four water-treatment plants in Selangor were shut down on Thursday (Sept 3).

Bernama news agency said 1.2 million consumer accounts were affected by the shutdown.

Selangor police chief Noor Azam Jamaludin said the four suspects, aged between 50 and 60, are brothers who have been managing the factory since their father's death, Bernama reported.

The Minister for Environment and Water, Tuan Ibrahim Tuan Man, vowed on Saturday that those behind the incident will be charged in court next week.

Public anger boiled over in recent days, especially after they learnt that the same company was fined RM60,000 (S$19,780) in March for the same offence.

"I want to emphasise here that the ministry will not compromise in enforcing the law against anyone in accordance with legal provisions," Datuk Tuan Ibrahim said, as quoted by Malay Mail online news.

Selangor and the federal territory of Kuala Lumpur share the same water resources, supplied by rivers and reservoirs in Selangor.

Selangor and KL are the most densely populated areas in Malaysia, with about seven million people.

Pictures on social media show thousands of people in many areas queuing up to fill up pails and bottles from water tankers.

Bottles of water sold in supermarkets flew off the shelves.

On social media, the some members of the public questioned why the government did not shut down the company after it committed a similar offence in March.

Others want the government to shut down the factory permanently.

Several dozen people from Parti Islam SeMalaysia turned up outside the factory in Rawang, Selangor, for a peaceful demonstration.

Reacting to the public anger, Selangor Menteri Besar Amirudin Shari said on Saturday that his state government will instruct the factory to vacate the land.

"We have asked the owner to rehabilitate the land. The building has to be demolished," he told a news conference, as quoted by Free Malaysia Today website.

He said the Selangor government has asked for water and electricity supply to the factory to be severed to prevent it from restarting operations.

Science, Technology and Innovation Minister Khairy Jamaluddin said the government should amend the Water Services Industry Act 2006 and the Environmental Quality Act to provide harsher penalties for those who pollute water sources.

"Water sources should be categorised under the security of the nation. It will be brought to the Cabinet, " he said in a tweet on Friday (Sept 4).

Officials from Pengurusan Air Selangor (Selangor Water Management) had said on Friday (Sept 3) that the four plants would likely only be able to serve consumers again from Monday.

But there was good news on Saturday, as the company said it has restarted the flow of water from its treatment plants to some homes beginning at noon, Malaysiakini news site reported.

The progressive restoration of water to consumers will take place until Monday (Sept 7) to 667 areas, or 51.6 per cent of the total affected areas.

Under the first phase, the majority of affected areas within the Kuala Selangor, Gombak, Kuala Lumpur and Hulu Selangor districts will see their water restored by the end of Monday.

The majority of areas in Petaling and Klang districts will only see their water restored under phase two, between Monday and Tuesday (Sept 7 and Sept 8).