Entire country left in the dark by massive breakdown.

ISLAMABAD -- Millions of citizens were left without power on Monday after a massive breakdown hit the fragile national grid in the morning and kept almost the entire country without electricity until late in the night.

Energy Minister Khurram Dastgir said on Monday night, more than 12 hours after the breakdown occurred, that officials had begun restoring electricity across the country. Power was beginning to return in parts Islamabad and Balochistan, he said.

The minister had earlier said that electricity across the country would be fully restored by 10pm on Monday after the breakdown - triggered by 'frequency variation' in the national grid - hit Pakistan.

In an interview with Geo News earlier, Mr Dastgir said the breakdown was not 'major'. He said, 'In winter, the demand for electricity reduces nationwide, hence, as an economic measure, we temporarily close down our power generation systems at night.

'However, when the systems were turned on in the morning today, frequency variation and voltage fluctuation was observed in the south of the country [...] somewhere between Dadu and Jamshoro [...] because of which power generating units shut down one by one,' he explained.

According to the Associated Press, officials said it all started when electricity was turned off during low-usage hours overnight to conserve fuel across the country, leaving technicians unable to boot up the system all at once after daybreak.

Sources said the initial voltage fluctuations forced the 'frequency sensitive' nuclear power plants, particularly the 1,100-megawatt K-2, to exit the system and go into 'island mode' as per their inbuilt security features, leaving the under-capacitated national grid to shut down in a cascading fashion across the country in a few moments.

But this belies repeated claims by successive governments since 2015 that safety equipment, techniques and best practices had been introduced to enable various parts of the grid and power plants to go into 'island mode' and shut down in case of any surge or plunge in electric supply, instead of crippling the entire country.

Prime Minister Shehbaz Sharif and the National Electric Power Regulatory Authority (Nepra) took 'serious notice of the countrywide breakdown' and ordered an investigation into the incident and sought a detailed report, respectively.

PM Shehbaz also constituted a three-member committee to investigate the matter and fix responsibility. The regulator reminded that it has also...