A massive blackout that plunged more than half of Cuba into the dark last month was caused by human error and unexpectedly high demand, says state power company Union Electrica.
The blackout, which began at 10:08 pm local time September 9, hit 10 of Cuba's 15 provinces, including Havana. Six provinces went totally dark for three hours.
The main cause was "an unexpected increase in top demand at 103 megawatts at a time later than peak demand hours", the company said.
It also said a technician who was told to disconnect certain circuits in the west "did not do so in time".
While rolling blackouts to save energy are not unusual in cash-strapped Cuba, a broad failure of the power grid like this one is rare.
Energy shortages are the Achilles heel of Communist-run Cuba's economy, which for more than a decade has been propped up by subsidised oil from ally Venezuela.
Throughout the blackout, Cubans searched the radio dial for information about the blackout, but state broadcasters did not report on the event for hours even though they remained on the air.
Power rationing was the norm in Cuba in the 1990s when the island was suffering acute economic distress following the collapse of the Soviet Union.
In 2004, a breakdown at Cuba's main power plant led to daily blackouts of 12 to 15 hours.