Power was restored in cities across Pakistan on Monday after the national grid collapsed on Sunday night, plunging most of the country into darkness for several hours.
Authorities said they had restored power in several areas of the largest cities, including Karachi, Lahore and Islamabad, though many regions in all four provinces continued to be without electricity.
Prime Minister Raja Pervez Ashraf had been monitoring the situation after the rare nationwide breakdown began at about 11.30 pm on Sunday night.
Officials blamed the phenomenon on technical problems at a major power plant in southwestern Balochistan province.
A privately run 1,200 MW thermal power plant of the Hub Power Company (HUBCO) in southwestern Balochistan province developed a fault and stopped generating electricity on Sunday night.
Islamabad Electric Supply Company CEO Javed Parvez said the load was transferred to the Mangla and Tarbela hydropower projects but they tripped.
The Mangla and Tarbela power projects had resumed generating electricity and efforts were being made to restore the supply of power to cities in phases, Parvez said.
According to television news channels, the outage affected almost 70 per cent of the country.
Power Secretary Rai Sikander told a news conference that over 5000 MW had been added to the national grid to restore power to several areas across the country, including Karachi, Lahore and cities in the northwest.
The government formed a four-member committee to probe the incident, which will submit its report in seven days.
Nationwide outages are not common in Pakistan though frequent power cuts lasting for several hours at a time have hit life across the country for the past three years.
The power cuts have crippled industry and triggered violent protests.