NEW DELHI: A massive power cut blacked out a vast swathe of northern India early Monday, affecting hundreds of millions of people in nine states including the capital New Delhi, officials said.

“The total northern grid collapsed at 2:40am (2110 GMT Sunday),” said D. K Jain deputy general manager at the Northern Regional Load Despatch Centre (NDLR).

“We are doing our best to stabilise the system,” Jain told AFP, adding that an investigation was underway into the cause of the mass outage.

The power cut severely disrupted transport networks, including trains and metro services, while traffic light systems also went down in some major cities causing snarls in the morning rush hour.

In a statement, the Power System Operation Corp. (PSOC), which manages the northern grid, said the “entire northern region,” which is home to 28 per cent of India's 1.2 billion population, had been affected.

The nine affected states were Delhi, Haryana, Himachal Pradesh, Jammu and Kashmir, Madhya Pradesh, Punjab, Rajasthan, Uttaranchal and Uttar Pradesh.

“Our priority is to restore power. Analysis of the cause will be done later. We have taken power from the eastern and western grid,” PSOC chief S.K. Soonee told AFP.

In New Delhi, the city's metro system shut down completely during the night and was operating only 25 per cent of normal services from 7:00am (0130 GMT).

“We expect a complete restoration of services in several hours,” said Delhi Metro spokesman Anuj Dayal.