The blackout began at about 11:50 p.m. local time on Saturday when power failures were reported in all major cities, including Islamabad, Lahore, Peshawar, Karachi and Rawalpindi.
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According to the National Transmission and Despatch Company, the system has tripped, and it may take a while to restore power.
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The blackout is caused after the frequency in the national power distribution system suddenly fell from 50 to zero, Federal Minister for Energy Omar Ayub Khan said in a tweet, adding that "we are trying to ascertain what caused the drop in frequency."
He said that attempts are being made to fire up the Tarbela power station which will lead to a sequential restoration of power supply.
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