India suffered its second huge, crippling power failure in two days Tuesday, depriving as much as half of the vast and populous country, or up to 600 million people, of electricity and disrupting transport networks. The first power grid collapse, on Monday, was the country's worst blackout in a decade. It affected seven states in northern India that are home to more than 350 million people.

But Tuesday's failure was even larger, hitting eastern and northeastern areas as well. Both blackouts cut power in the Indian capital, New Delhi.

The power companies that operate the affected electricity grids reported Tuesday's collapse on their websites.

With about 1.2 billion people, India has the second-highest population of any country, behind China.

At least 300 trains have been held up in the affected regions, said Anil Kumar Saxena, a spokesman for Indian Railways.

Miners in the Burdwan District of West Bengal state have also been hit by the blackout.

The district's top administrator, O.S. Meena, told CNN that 150 coal miners were working underground when the outage happened, stopping lifts.

Authorities switched to emergency supplies to run elevators to bring the miners up, and more than 60% have been brought above ground, he said.

"The others will be brought up very soon. All are safe," Meena said.

Authorities have urged people not to panic about the safety of the miners.

The two consecutive days of disruption are embarrassing for India, a nation growing in international stature and the third-largest Asian economy.

The power companies said they were working to restore service. It was not immediately clear whether the blackouts were partial or total in the different regions.

Monday's grid failure struck in the early morning. Residents spent the rest of the night drenched in sweat amid humid weather, and many backup power systems had run out by daybreak. Power was partially restored after about six hours, authorities said.

That blackout left passengers stranded at train stations, and signal failures caused traffic snarls that choked the Indian capital's already congested roads during office hours.

Indians, however, have not been strangers to power cuts, which become more common during the summer when demand shoots up.

Some of the increased demand this summer has been caused by farmers using more energy for irrigation and other tasks, in part because monsoon rains have been delayed. People are also using air conditioning units more.

The Indian power minister, Sushilkumar Shinde, has ordered an investigation into Monday's outage. He said the last time that an entire grid failed in north India was 10 years ago.

He said that the reason for the latest blackouts is not yet known but that some states, particularly those with a lot of agricultural activity, may have been using more than their share of energy.

Observers say the crisis has exposed the need for India to update its infrastructure to meet the power needs of businesses and the country's growing population.