The colour of Lukha river in East Jaintia Hills district and Myntdu river in West Jaintia Hills district has changed to a bright sky blue, "an annual occurence at this time of the year", according to locals.
The Meghalaya State Pollution Control Board in its 2012 report blamed "mine run-off" and acid effluents from coal mines as the main causes of water pollution in the area.
MSPCB member secretary J H Nengnong said the Board would be deputing officials to collect water samples from the affected rivers for conducting various tests.
Prominent environmentalist from the area H H Mohrmen demanded thorough and independent tests to be conducted to find out the actual reason.
More From This Section
"In most parts of the rivers, we could find fine dust-like particles at the bottom of the rivers," he said pointing out that the fly ash released from cement factories located a few kilometers from the water bodies could be one of the probable reasons.
In the past years, scores of dead fish were seen floating in the river, but local people told PTI said no dead fish were detected this year.
Local anglers who frequented the rivers in eastern Meghalaya said that another river Myntdu also started to change its colour.
The Meghalaya Electricity Corporation Ltd (MeECL) which has a "run-of-the-river power" base at Leshka confluence has also reported that high acidic content of the water in the river is corroding machinery parts.
With mining and transportation of coal banned since April by the National Green Tribunal, the coal lying in depots across the two districts is a concern.