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Half of India's thermal power stations have less than a week's supply of coal on hand, according to weekly data, the lowest level since mid-2012 when millions of people were left without power in one of the world's worst blackouts.
There was a sharp fall in power output on Thursday from a plant in Gujarat that left the country more than 9,000 megawatts short of peak demand, according to two officials at the state grid operator.
Any grid collapse would cast doubt on the crisis management skills of the new government led by Prime Minister Narendra Modi, whose achievement in ensuring 24-hour power supplies in his home state of Gujarat helped him to election victory in May.
Commenting on Thursday, Power and Coal Minister Piyush Goyal said: "I don't know about the possibility of a breakdown ... There is a problem, I think, with many of the coal supplies."
The figures, released by the Central Electricity Authority (CEA) on Tuesday and accessed by Reuters on Friday, showed that 50 of India's 100 thermal power stations had enough coal to last less than seven days.
Taken as a whole, India's thermal power generators have six days of supplies - far short of the 15-30 days set as an operating norm by the CEA.
Plants are running short of the fuel due to lower supplies from Coal India Ltd, the state behemoth that has become a byword for inefficiency.
Cautious moves to open up coal mining to competition have, meanwhile, been thrown into chaos by a Supreme Court ruling this week that all coal block allocations since 1993 were illegal.
