The mineral-rich Jaintia Hills district of Meghalaya faces an acute drinking water crisis as major rivers there have been declared "unfit" for human use due to high level of acidity caused by unscientific mining.

The rivers close to coal mining areas and cement plants have acquired a blue colour over the last five years-- a phenomenon baffling even environmental scientists of the state.

The Delhi-based Central Laboratory of the Central Pollution Control Board (CPCB), which conducted an analysis of water samples collected from these rivers, said the water was highly 'acidic', rendering it unsuitable to support life forms.

The latest report, submitted by the Meghalaya State Pollution Control Board to the state government and CPCB, Delhi, said, "Mine run off from coal mines are the major probable causes of water pollution in the area."

"The undesirable change in water quality affects a variety of flora and fauna of the rivers. Fish, as such, are susceptible to acidity and low pH values are unsuitable for most aquatic organisms," the report said.

Five years back, river Lukha in the Khliehriat sub-division turned blue and all aquatic life, including fish, died and were found floating in the river.