India's electric grid is old and deteriorating.Reuters

Half on India was plunged into darkness on Tuesday, as power grid failure hit North India for the second consecutive day in one of the worst blackouts since 2001.

India's northern and eastern power grids collapsed affecting over 600 million people in the second day of electricity chaos.

"We are busy with the revival right now... Both the Northern and Eastern grids have collapsed. Please allow us to address the problem," V.K. Agrawal, the general manager of the northern grid, told Agence France-Presse (AFP).

The eastern grid, which collapsed on Tuesday afternoon, covers the states of West Bengal, Bihar, Jharkhand, Sikkim, and Odisha. Power supply has affected the northern as well as the eastern region of the country including Delhi, Uttar Pradesh, Haryana, West Bengal, Assam and Punjab.

According to latest reports, power ministry sources said that the eastern grid is slowly restoring and power has been completely restored to Odisha. Also, power has been restored in 20 percent of East India and in 50 percent of the country's northeast.

Meanwhile, emergency services in Delhi have resumed partial services on all lines of the Delhi Metro, Also, some railway lines have also started working, Indian daily Firstpost reported.

"This is a big crisis. We are working to restore power. Many states overdraw power and this has caused a complete collapse in eastern and northern India," AFP quoted a senior official at the ministry of power in New Delhi as saying.

Power Minister Sushil Kumar Shinde confirmed the news to the media and also said that power will be restored in an hour.

The power outages in North India were first reported early Monday, with Delhi and seven other northern states facing a mass blackout for over 15 hours.

Over 300 million people were affected and hundreds of passengers were left stranded at metro stations due to disruption of train services. The grid disturbance in the northern region happened at around 2.35 am.

By Monday afternoon power supply was restored in a phase-by-phase manner in Delhi and some parts of Uttar Pradesh. Other states like Rajasthan, Punjab and Jammu and Kashmir were thrown into darkness well into Monday evening.