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,

Electricity has returned to most of Spain and Portugal but with continued disruptions on the second day after an unknown failure caused a massive blackout across much of western Europe.

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