NEW DELHI — India's energy crisis cascaded over half the country Tuesday when three of its regional grids collapsed, leaving 620 million people without government-supplied electricity for several hours in, by far, the world's biggest-ever blackout.

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The massive failure — a day after a similar, but smaller power failure — has raised serious concerns about India's outdated infrastructure and the government's inability to meet its huge appetite for energy as the country aspires to become a regional economic superpower.