A massive grid failure has left more than 600 million people in India without power, the second large-scale outage to hit the country in as many days.

Tuesday's blackout hit the northern and eastern parts of the country, including major cities like New Delhi and Kolkata. It brought rail service to a halt and knocked out traffic signals in the capital.

Power companies had restored service to northern India late Monday after an outage that affected more than 300 people, but the grid collapsed again early Tuesday afternoon.

Limited power failures are common in India, but analysts say such large-scale outages highlight the deficiencies in the country's infrastructure as it strives to become an economic superpower.

India relies heavily on coal to produce electricity for its more than 1.2 billion people.