The electricity supply to India's capital, Delhi, has been largely restored after a two-day blackout across much of the country.
More than 600 million people across India were affected by the power cut after three power grids collapsed, one for a second consecutive day.
Transport networks ground to a halt with hundreds of trains stranded and water supplies interrupted.
Full power is not expected to resume until some time on Wednesday.
The breakdowns in the northern, eastern, and north-eastern grids affected at least 20 of India's 28 states.
In Delhi, Metro services were halted and staff evacuated trains. Many traffic lights in the city failed, leading to massive traffic jams.
Other areas affected included Delhi, Punjab, Haryana, Uttar Pradesh, Himachal Pradesh and Rajasthan in the north, and West Bengal, Bihar, Orissa and Jharkhand in the east.
In eastern India, around 200 miners were trapped underground as lifts failed, but officials later said they had all been rescued.
One shopworker in Delhi, Anu Chopra, 21, said: "I can understand this happening once in a while but how can one allow such a thing to happen two days in a row?
"It just shows our infrastructure is in a complete mess. There is no transparency and no accountability whatsoever."
By late on Tuesday, officials said the north-eastern grid was fully up and running. The northern grid was running at 75% capacity and the eastern at 40%.
Power has largely been restored to Delhi and much of the north of the country, and the country's railway network has started moving again, although a full service is not expected for many hours.
However large swathes of the country are still without electricity.
In a statement on national TV on Tuesday evening, Power Minister Sushil Kumar Shinde blamed the crisis on states taking more than their quota of power from the national grid.
He said he had appealed to states to stop this and instructed his officials to penalise those states which did.
But officials in Uttar Pradesh, one of the states blamed in the Indian media, said there was "no reason to believe" they were at fault.
Anil K Gupta, the chairman of the state's power company, called for "further investigation to ascertain the real cause".
The power minister of Haryana state, Captain Ajay Singh, was quoted by NDTV as saying his was not the only state with overdraw from the grid.
"We are not to be blamed for the technical snag that tripped the grid," he said. "We are simply being blamed for what everyone does."
Also on Tuesday it was announced that Mr Shinde had been promoted to the post of home minister, in a widely anticipated cabinet reshuffle.
He has been replaced by the current corporate affairs minister, Veerappa Moily.
The chairman of the Power Grid Corporation of India, R N Nayak, said on Tuesday that the exact cause of the power cut was unclear, but that it appeared to be due to the "interconnection of grids".
He told Indians they were "in safe hands", saying: "We have been running this grid for decades. ... Please trust us."
Power cuts are common in Indian cities because of a fundamental shortage of power and an ageing grid - the chaos caused by such cuts has led to protests and unrest on the streets in the past.
But the collapse of an entire grid is rare - the last time the northern grid failed was in 2001.
India's demand for electricity has soared in recent years as its economy has grown but its power infrastructure has been unable to meet the growing needs.
Correspondents say unless there is a huge investment in the power sector, the country will see many more power failures.