Power outage in Spain and Portugal still a mystery, but leaders vow to solve it and prevent a recurrence

Spain's government has set up a special commission to figure out what caused the massive power outage that hit virtually the entire country, Prime Minister Pedro Sánchez announced Tuesday, stressing that no potential causes had been ruled out. He also joined the wider European Union in vowing that everything necessary would be done to prevent a recurrence of the electricity grid failure, which ground most of the Iberian Peninsula — composed of Spain and neighboring Portugal — to a halt and left people in the dark until Tuesday morning.

"All the necessary measures will be taken to ensure that this does not happen again," Sánchez said during a news conference in Madrid, just hours after the lights came back on.

Monday's still-unexplained power outage was the most severe ever to hit Spain and Portugal, which have a combined population of around 60 million people. According to The Associated Press, Spain's roughly 49 million inhabitants saw their country's power generation drop by around 15 gigawatts — roughly 60% of the typical real-time demand in the nation — in the space of just five seconds, starting just after noon local time on Monday.