More than 1.2 million Malaysians were without piped water Tuesday, authorities said, as contamination from a landfill forced a treatment plant to close.

National water distribution company Syabas said it was sending water trucks and tanks to residents in the affected area in Selangor state, which surrounds Kuala Lumpur, and also trying to redistribute water from other plants.

It said the plant, run by the state water consortium, was shut down early on Tuesday as part of an emergency action plan once the contamination was discovered.

"The contamination from a nearby landfill leached into the Semenyih river which provides the raw water being fed into the treatment plant," Abdul Halem Mat Som, Syabas corporate communications executive director, told AFP.

He said authorities found ammonia contamination of 6.41 milligrams per litre, more than four times the health ministry's acceptable level of 1.5 milligrams.

"As the plant treats about 600 million litres of water daily to supply 300,000 households, or more than 1.2 million residents in the area, it had to be shut down so that action can be taken to stop the contamination," he said.

"Once we have carried out a full investigation, we will know how best to rectify the situation and for how long the water treatment plant will be closed but this will take some time. The contamination is quite extensive," he added.