A power outage darkened Pakistan's largest city and commercial capital for almost a day Thursday, leaving millions of people without fans or air conditioning during the summer heat, officials said.

Aisha Arabi, spokeswoman for the Karachi Electricity Company, said power had been restored to most of the city but warned that sections would face further outages in the near future under a "load sharing" plan to deal with an ongoing power shortage.

Earlier Thursday, Minister for Power Raja Ashraf told parliament that the crisis, which began Wednesday night, was caused by a technical fault that would be fixed in a few hours.

Karachi is known as Pakistan's "city of lights," but many residents spent a sleepless night in summer heat. Essential services were suspended, and major industries were shut.

Pakistan is experiencing a major electricity crisis, with many people facing up to 12-hour cutoffs due to soaring demand and a lack of investment in generating capacity.