JOHOR BARU (THE STAR/ASIA NEWS NETWORK) - Some 1.8 million residents in southern Johor have been struck by a major water supply disruption, after three water treatment plants were shut down due to high ammonia levels found in raw water from Sungai Johor.

Operations at three water treatment plants - the Semangar, Sungai Johor and Tai Hong water treatment plants - were stopped on Saturday (Oct 28) after a high level of ammonia was recorded.

SAJ Ranhill's corporate communications head Jamaluddin Jamal said that residents in at least three districts, namely Johor Baru, Kulai and Kota Tinggi, have been affected by the shutdown.

He said that the ammonia level of 2.75 parts per million (ppm) recorded late on Friday night had not reduced as of 4.30pm on Saturday. The level is much higher than the Health Ministry's permitted level of 1.5ppm.

"Water quality is our priority, thus we decided to halt operations to treat raw water from the river.

"This is not the first time high levels of ammonia have disrupted water supply. We have recorded three major incidents this year alone," he said in a statement on Saturday.

Jamaluddin said the situation could be prolonged for up to two days, if ammonia levels do not drop.

"We urge the public not to panic and to use water wisely," he said, adding that affected residents could contact its hotline at 1800-88-7474 for assistance.