A massive power breakdown plunged the entire Pakistan into darkness minutes before midnight on Saturday, Energy Minister Omar Ayub confirmed in a statement.
The blackout was initially reported on social media by residents of major urban centres such as Karachi, Lahore, Islamabad and Multan, as well as other towns and cities across the country.
Hours later, the energy minister tweeted that power supply was being restored to cities in phases, starting with Islamabad, but most parts of the country were still affected by the breakdown.
According to Ayub, the power breakdown was caused after the frequency in the national power distribution system suddenly fell from 50 to zero.
He said the reason for the frequency dropping was being investigated, adding that attempts were being made to fire up the Tarbela power station which will lead to a sequential restoration of power supply.
"People are urged to remain patient," the minister wrote.
Ayub said all technical teams had reached their respective stations, adding that he was personally supervising the restoration work as the federal power minister.
He said citizens would be kept updated on the restoration efforts periodically.
Some time later, the Ministry of Energy spokesperson, tweeting from the ministry's official Twitter handle, said that according to initial reports, the Guddu power plant developed a fault at 11:41pm on Saturday night.
"The fault caused the country's high transmission lines to trip, which in turn caused the system frequency to drop from 50 to 0 in less than a second.
The drop in frequency caused power plants to shut down."
The spokesperson added that the units of Tarbela and Warsak power houses had been fired up, adding that power was being restored to the transmission system.
"Phase-wise restoration of power will be initiated soon," they said. "Once the initial frequency is met, the restoration work speeds up."
Earlier, Federal Information Minister Shibli Faraz had said that the breakdown had been caused by a "technical fault" in the National Transmission and Despatch Company (NTDC) system. "System is being restored," he tweeted.
Special assistant to the prime minister Shahbaz Gill also said that the energy minister and his entire team were working on the issue. He said citizens would be updated on the situation soon.
Meanwhile, Karachi Electric (KE) said in a statement on Sunday that its teams have "started work on restoring electricity [supply] from its own system".
Power supply has been restored in some areas of Valika, KDA, Federal B, Airport One and Gulistan-i-Jauhar, a spokesperson for KE said.
Engineering teams are making "full efforts" to restore electricity supply, the spokesperson added.
Copyright: Dawn/ Asia News Network (ANN)