A massive power breakdown has hit India for a second day running; leaving more than 300 million people without electricity in one of the worst blackouts to hit the country in more than a decade.

The lights in Delhi and seven other states had not been restored by the morning rush-hour, leaving the capital's workers sweltering overnight and stranded at metro stations.

The Indian power minister official explained the situation and what had happened.

"There was overdrawing of power as the demand peaked. As a result, two to three grid tripped simultaneously. Gradually we would come to know about the reasons. Presently we are engaged in restoration of the electricity supply."

After Monday's power cut, engineers managed to restore electricity to the northern grid by the evening, but at 0735 it had collapsed again. The eastern grid failed around the same time. The two grids together serve more than half of India's population. But the collapse of an entire grid is rare - the last time the northern grid failed was in 2001.

Written and presented by Ann Salter