Several cities and towns across Pakistan plunged into darkness overnight following a major technical fault in the country’s power generation and distribution system, the energy minister said on Sunday.

The power outage was reported shortly before midnight almost simultaneously in many cities. Residents of Karachi, Rawalpindi, Lahore, Islamabad, Multan and others faced the blackout.

Pakistan energy minister Omar Ayub Khan, along with information minister Shibli Faraz, told reporters that the power supply snapped at 11.41pm on Saturday after a technical fault at the Guddu power plant in Sindh province.

“It had what we call a ‘cascading effect’ and shut down the power system, choking about 10,320 megawatt of electricity,” Omar said, adding that it was the precise amount of energy needed for the entire country during the winter nights.

The minister said the power plant’s safety systems started shutting off automatically soon after it developed a fault, the Express Tribune reported.

Omar said Prime Minister Imran Khan had been informed of the situation, the report said. The energy minister said technical teams were working to fully restore power supply.

According to Omar, electricity supply had been restored fully or partially in many cities such as Islamabad, Rawalpindi, Lahore, Multan, Karachi and Faisalabad but it would take some time before the restoration of normal supply.

He said it was still unknown what exactly triggered the shutdown that caused the drop in the system frequency from about 50 to zero.