India's energy crisis cascaded over half the country Tuesday when three of its regional grids collapsed, leaving hundreds of millions of people without government-supplied electricity in one of the world's biggest-ever blackouts.

The outages left about 620 million people in the dark in about 20 states, though the Times of India newspaper reported that by 7:30 p.m. local time, around 75 per cent of the power had been restored in northern areas and about 40 per cent of eastern India was back to normal.

Hundreds of trains were stalled across the country and traffic lights went out, causing widespread traffic jams in New Delhi. Electric crematoria stopped operating, some with bodies half burnt, power officials said. Emergency workers rushed generators to coal mines to rescue miners trapped underground.

The Times of India reported that about 200 miners in the northeast were rescued in West Bengal in the evening, while another rescue operation was underway at Jharkhand to help 65 others trapped in a coal mine.

Commuters wait for buses outside a Metro station after Delhi Metro rail services were disrupted following power outage in New Delhi on Tuesday. (Rajesh Kumar Singh/Associated Press)

The massive power failure — a day after a similar, but smaller power failure — has raised serious concerns about India's outdated infrastructure and the government's inability to meet its huge appetite for energy as the country aspires to become a regional economic superpower.

Power Minister Sushil Kumar Shinde blamed the new crisis on states taking more than their allotted share of electricity.

"Everyone overdraws from the grid. Just this morning I held a meeting with power officials from the states and I gave directions that states that overdraw should be punished. We have given instructions that their power supply could be cut," he told reporters.

The new power failure affected people across most of India's 28 states — more than the entire population of the European Union plus Turkey. The blackout was unusual in its reach, stretching from the border with Myanmar in the northeast to the Pakistani border about 3,000 kilometres away.

Familiarity with frequent blackouts

Its impact, however, was softened by Indians' familiarity with frequent blackouts and the widespread use of backup generators for major businesses and key facilities such as hospitals and airports.

R.N. Nayak, chairman of Power Grid Corp., which runs the nation's power system, had said he hoped to have full power restored by 7 p.m. local time in the northeast.

The outages came just a day after India's northern power grid collapsed for several hours. Indian officials managed to restore power several hours later, but at 1:05 p.m. Tuesday the northern grid collapsed again, said Shailendre Dubey, an official at the Uttar Pradesh Power Corp. in India's largest state. About the same time, the eastern grid failed and then the northeastern grid followed, energy officials in those regions said. The grids serve more than half India's population.

In West Bengal, express trains and local electric trains were stopped at stations across the state on the eastern grid. Crowds of people thronged the stations, waiting for any transport to take them to their destinations.

Chief Minister Mamata Banerjee said it would take at least 10 to 12 hours to restore power and asked office workers to go home.

Utilities unable to meet growing needs

"The situation is very grave. We are doing everything to restore power," West Bengal Power Minister Manish Gupta said.

New Delhi's Metro rail system, which serves about 1.8 million people a day, immediately shut down for the second day in a row. Police said they managed to evacuate Delhi's busy Rajiv Chowk station in under half an hour before closing the shutters.

S.K. Jain, 54, said he was on his way to file his income tax return when the Metro closed and now would almost certainly miss the deadline.

India's demand for electricity has soared along with its economy in recent years, but utilities have been unable to meet the growing needs. India's Central Electricity Authority reported power deficits of more than eight per cent in recent months.

The power deficit was worsened by a weak monsoon that lowered hydroelectric generation and kept temperatures higher, further increasing electricity usage as people seek to cool off.

But any connection to the grid remains a luxury for many. One-third of India's households do not even have electricity to power a light bulb, according to last year's census.