The nature of fault was not known exactly but it plunged about 80 per cent country into darkness, the fourth major breakdown of the system within the past one month.
There were contradictory statements about the reason for the breakdown.
An official of water and power ministry said that the tripping of Guddu power plant's transmission lines affected the 500 KW power line from the national grid, forcing Jamshoro and Bin Qasim power stations to shut down.
Deputy Minister for Water and Power Abid Sher Ali said that transmission lines in Balochistan's Nasirabad district were blown up by militants which caused the power failure.
The authorities were working non-stop
The crisis came on the heels of the recent petrol shortage which paralysed the country for about two weeks.
Prime Minister Nawaz Sharif who was already reeling from the petrol criticism, faced another barrage of outrage.
He took notice of the worst-ever power breakdown and issued instructions for the immediate resumption of power supply on an emergency basis.
The breakdown hit amid rumours that the country's power crisis would be exacerbated as a result of acute shortage of furnace oil.
Due to shortage of furnace oil, the power production from Jamshoro power plant was decreased to 170 MW from 570 MW and from 700 MW to 360 MW at Muzaffargarh plant, as Faisalabad power plant has suspended power generation.
Currently the country demand of electricity is around 14,000 MW as compared to total generation of 7,000 MW.