NEW DELHI -- India's top electricity official says power has been restored across the country after a major system collapse led to the worst blackout in history.
An estimated 620 million people were without power after India's northern, eastern and northeastern grids cascaded into failure Tuesday afternoon.
Electricity workers struggled throughout the day to get power back to the 20 affected states. They restored most of the system in the hours after the crash.
Power Minister Veerappa Moily told reporters Wednesday morning that power had been fully restored.
The government has ordered an investigation into what caused the crisis.
Moily said he did not want to point fingers. Other officials said the crisis might have been caused by states drawing too much power from the grid but some analysts dismissed that explanation.