NEW DELHI – A massive breakdown of India’s electricity grid cut power to 370 million people in seven northern states Monday, halting trains, cutting water supplies and creating commuter mayhem.

The crisis, which hit soon after midnight, knocked out power to the states of Punjab, Haryana, Himachal Pradesh, Rajasthan, Jammu and Kashmir and Uttar Pradesh, which has more people than Brazil. By some accounts, it was the worst blackout in India since 2001.

As officials struggled to contain the damage, electricity was diverted from adjoining states and priority was given to hospitals, water-treatment plants and transport systems, including the subway system in Delhi, the national capital territory, which has the status of a state. By late afternoon, the government reported that power had been restored.