Power has been restored to tens of millions of people across almost all of Spain and Portugal, but disruptions to transport services were expected to stretch into a second day as questions mount over what caused a massive blackout.

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

BARCELONA, Spain (AP) — A blackout brought much of Spain and Portugal to a standstill Monday, halting subway trains, cutting phone service and shutting down traffic lights and ATM machines for the 50 million people who live across the Iberian Peninsula.