IPOH, Nov. 17 -- The cause of the recent river water discolouration in Sungai Perak, Gerik, remains unknown.

State Science, Environment and Green Technology Committee chairman Teh Kok Lim said investigations into why the river turned blue are still ongoing, with the actual source yet to be determined.

"Authorities did find signs of (toxic substances) overflow, but could not determine where it came from. The actual source has not been identified," he said.

Teh told reporters this when asked for an update on the investigation after attending the Majlis Anugerah Inovasi Perak at the Perak Darul Ridzuan Building here.

He said traces of the suspected overflow are now difficult to detect.

"The water that overflowed can no longer be traced....