The sweeping power outage that hit Spain and Portugal this week has raised questions about the electricity grid in a region not normally known for blackouts. Monday's outage, one of the worst ever in Europe,

Red Eléctrica, Spain’s electricity grid operator, ruled out a cyberattack, human error or unusual weather. Experts say it could take weeks to determine the cause.

A widespread power outage hit Spain and Portugal, affecting millions of people who live across Europe's Iberian Peninsula.