More than half of India has been left without power after a massive power breakdown has hit the country for a second day running.
Indian officials said the northern and eastern grids had both collapsed. All Delhi metro services have been halted and staff is trying to evacuate trains.
Monday’s power failure caused severe disruption and travel chaos across northern India.
It was unclear why the grid collapsed but the power minister said some states may have been taking too much power.
Sushil Kumar Shinde said power would be restored in “another 90 minutes”.
After Monday’s cut, engineers managed to restore electricity to the northern grid by the evening, but at 01:05 p.m. on Tuesday, it collapsed again.
More than half of India has been left without power after a massive power breakdown has hit the country for a second day running
The eastern grid failed around the same time, officials said.
“Both the northern and eastern grids have collapsed. Please allow us to address the problem,” AFP news agency quoted VK Agrawal, the general manager of the northern grid, as saying.
The two grids together serve more than half of India’s 1.2 billion people.
The breakdown has hit a large swathe of the country including Delhi, Punjab, Haryana, Uttar Pradesh, Himachal Pradesh and Rajasthan states in the north, and West Bengal, Bihar, Orissa and Jharkhand in the east.
An official in Orissa said the blackout in the eastern grid had been triggered by a fault and could take several hours to resolve.
Railway officials said more than 350 trains were stranded, and hospitals and essential services were running on backup generators.
Across West Bengal, power went at 13:00 and all suburban railway trains on the eastern railways ground to a halt from Howrah and Seladah stations.
However, the city is not badly affected as it is served by a private electricity board, our correspondent adds.
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.
Costa Allegra, the Italian cruise ship left adrift in the Indian Ocean near Seychelles with more than 1,000 people on board following a power failure, has been taken in tow.
A French fishing vessel is taking the Costa Allegra to a small island in the Seychelles, where it is expected to arrive on Wednesday.
A fire in the ship’s generator room on Monday caused it to lose all power.
Costa Allegra is from the same fleet as the Costa Concordia, which capsized off the Italian coast in January, killing 32.
The ship is being towed to Desroches island, near Alphonse island, at the south-west end of the Seychelles.
Once there the passengers will be disembarked to the one hotel on the island, and then await transfer by air to the main Seychelles island of Mahe.
That process could prove lengthy, since only planes with a capacity of 20 passengers can land on Desroches.
Tugs sent from Mahe were due to meet the Costa Allegra at around 09:00 GMT.
A French fishing vessel is taking the Costa Allegra to a small island in the Seychelles, where it is expected to arrive on Wednesday
The vessel has no air-conditioning or cooking facilities and an emergency generator powering the radio “could fail at any minute”, the Italian coast guard says.
Earlier, Commander Cosimo Nicastro, from the Italian coast guard, confirmed that the French-registered ocean-going trawler had reached the ship.
The ship’s owner, Costa Cruises, has stressed that the Allegra – which had been drifting about 32 km (20 miles) from Alphonse island – is steady and conditions are safe. No-one has been injured, officials said.
Costa Cruises says it is liaising with passengers’ families via their emergency contact numbers, and has reached two-thirds of them. Contact has been made with the relatives of all the crew.
Italian authorities have directed three merchant ships and another fishing vessel towards the stricken cruise ship.
Authorities in the Seychelles earlier said that a plane had flown overhead and reported that the ship did not appear to be in danger.
Costa Allegra is at the southern end of the seas that are vulnerable to attacks by Somali pirates.
The ship sailed with nine armed guards on board, and more are stationed on the French fishing vessel. Pirates in the area have never seized a cruise ship.
A government plane is also patrolling overhead.
Costa Cruises said that the ship sent out a distress signal when the fire broke out, and all passengers and crew not involved in fighting the fire assembled at the muster stations.
Most electric lights on board the ship are off as the batteries are being used to keep essential machinery going.
A spokesman said the situation on board was calm.
There are 636 passengers and 413 crew on board the Costa Allegra, which left Madagascar on Saturday.
It was due to arrive in the Seychelles on Tuesday.
Further destinations on its itinerary include Alexandria and Naples.
A facility on Costa Cruises’ website allowing people to track the Allegra’s position says that “data transmission is temporarily suspended”.
The company says the Costa Allegra received its regularly scheduled maintenance in dry dock in October 2011.
The Costa Concordia ran aground off the Italian island of Giglio on 13 January.
The Concordia’s captain, Francesco Schettino, has been accused of manslaughter, causing a shipwreck and abandoning ship before all those aboard were evacuated. He denies any wrongdoing.