Before dawn, power was gradually returning to several regions across Spain and Portugal as the nations reeled from the still-unexplained widespread blackout that had turned airports and train stations into campgrounds for stranded travelers.

BARCELONA, Spain (AP) — A blackout brought much of Spain and Portugal to a standstill Monday, halting subway and railway trains, cutting phone service and shutting down traffic lights and ATMs for millions of people across the Iberian Peninsula.