Pakistan's government has ordered an inquiry into the cause of a nationwide power cut that plunged the country into darkness for a few hours.
The electricity network broke down on Sunday after a power plant in south-western Balochistan province developed a technical fault, officials say.
The cities of Islamabad, Lahore, Peshawar and Rawalpindi were among those affected.
Power cuts are common in Pakistan, but a nationwide failure is rare.
A breakdown at the Balochistan plant - which generates 1,200 megawatts of electricity daily - triggered other plants to shut down, water and power ministry official Rai Sikandar said.
"It was a technical fault in one of our power plants and not in the national grid," he told Agence France-Presse news agency.
Blackouts are nothing new in Pakistan because of chronic power shortages, with many areas having no electricity for several hours a day, says the BBC's Orla Guerin in Islamabad.
But on Sunday night, the darkness that suddenly enveloped the country caused some to fear there had been a terrorist attack or a military coup, our correspondent adds.
Power is being restored on a phased basis, officials say.