The seven, aged between 27 and 38, were arrested yesterday for allegedly committing mischief which caused a diminution of the water supply in the incident on Thursday.

Kuala Muda district police chief ACP Adzli Abu Shah said those remanded for six days from today included four Indonesian workers and another Malaysian.

He said preliminary investigation found that the pollution occurred due to installation of a jacking pipe at a project site about 100m from the Jeniang water treatment plant.

Three barrels containing diesel, for use by an excavator and generator, were found at the site, he said.

He said there were traces of diesel in the ground and it was believed it flowed into a drain before entering Sungai Muda.

On Thursday, Syarikat Air Darul Aman (SADA) CEO Mohd Suhaimi Mohd Jusoh said water supply to 34,200 households in Sik and Kuala Muda had been disrupted when the water treatment plants at Jeniang Baru, Jeniang Lama and Sungai Pau were forced to temporarily shut down.