KUALA LUMPUR: A colourant discharge is believed to be the cause behind Sungai Gong's inky water, the Selangor Water Management Authority (Luas) said.
Luas also said a probe into the river's water quality also found foaming effluents from sewage treatment plants of Indah Water Konsortium (IWK) GBK 134 area 5 at the Rawang industrial area.
An in-situ sampling at the area found ammonia at 5.2mg/l and TSS (total suspended solids) at 47mg/l.
Lusas said IWK had since halted both water flow from the incoming pump and the discharge of effluents.
Luas had begun looking into the problem following a report by the Gombak Irrigation and Drainage Department (DID) at 12.11pm today.
Initial investigations at the DID flood detention pond inlet found no odour emanating from the water.
Luas then activated Code Yellow to halt operations in the main water treatment plants located at the downstream of Sungai Selangor.
Luas also held a joint-investigation with Air Selangor at the river monitoring station in Rawang Country Homes but found no oil stains or odour, despite the water's inky colour.
Investigations at Sungai Sembah, which discharges water into Sungai Selangor also found no odour or traces of colourants.
Luas has confirmed that water treatment plants are in operation and no water disruption has occurred due to the incident and said that it would continue monitoring the situation.