The Johor state government said it was still investigating the cause of the contamination, first detected at 1.30pm yesterday.

State exco in charge of utilities Jimmy Puah Wee Tse said ammonia levels have dropped due to dilution efforts.

He said state water authority Johor Water Regulation Body (Bakaj) and state water supply company Ranhill SAJ Sdn Bhd are meeting this afternoon to discuss the problem.

“Further updates will be given after the meeting this afternoon,” he told FMT.

Puah said at this stage, authorities have ruled out sabotage.

“I hope all users can bear with the interim situation and we will work around the clock to ensure full water recovery to affected areas.”

In March last year, some 6,000 people including school children in Pasir Gudang were affected by chemicals polluting Sungai Kim Kim, which forced the temporary closure of 111 schools. Four people were charged with the crime of chemical waste dumping.