A major power outage caused a blackout in Northern India, the worst since 2001, and severely hit normal life in eight states since late Sunday night, following the collapse of the the northern power grid.

The power that went out at 2.30 a.m. Sunday in New Delhi, Punjab, Haryana, Himachal Pradesh, Uttar Pradesh, Jammu and Kashmir and Rajasthan, affected the water supply and the industrial and domestic power supply.

Power supply lines to hospitals, transport and those for water supply are being restored on a priority basis.

The outage brought metro rail services in Delhi to a standstill, resulting in a commotion of thousands of rush-hour passengers. However, services were resumed on all six lines by 8.45 a.m. Monday after almost three hours.

Train services were disrupted in Punjab, Haryana and Chandigarh, leaving a large number of passengers stranded. Major trains like the Shatabadi Express, the Chandigarh-Chennai train, Sadbhawna Express, Sachkhand Express and the Rajdhani Express were hit by the outage. Some trains were stranded mid-way as the electric engines stopped functioning following the massive power cut. The railway signal system was shut at a number of places due to the power failure.

The airport services at the New Delhi airport are unaffected and are operating using a backup, which is expected to last up to 48 hours.

Delhi's All India Institute of Medical Sciences (AIIMS) and the Prime Minister's house have switched to hydel power.

Power returned to some parts of the region by 9 a.m. Monday. The power ministry officials said that most of the supply will be restored by Monday noon in Delhi.

Six water treatment plants in Delhi were shut since the grid collapse, of which five are now operational.

Delhi's traffic management system was affected leading to a chaos on the roads. The city's traffic police have deployed more policemen to restore normalcy.

The Power Minister, Sushilkumar Shinde, said most electricity supplies will become operational in the day.

"Some fault has occurred near Agra," Shinde said. "This is an accident. Already, teams have rushed to the spot. Almost 60 per cent of supplies were restored by 11 a.m. on Monday. Remaining would be restored in another couple of hours."

"It has happened after 10 years. Nearly, 8,200 megawatts of supplies from hydropower has also been flowed in the grid since morning. Power supplies have been taken from the Eastern Grid also," Shinde said.

The U.P. Power Corporation Limited (UPPCL) officials told the United News of India (UNI) that the failure of the transmission lines, following the collapse of the northern power grid, led to auto shutdown of all power generations across northern India.