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

Electricity returned to nearly all of Spain almost 18 hours after a blackout there and in neighboring Portugal. The cause of the outage was unclear.

Millions were plunged into darkness in Europe on Monday as a massive power outage impacted parts of Spain, France and Portugal. The blackout wreaked havoc on travel across the three countries, and the impacts extended beyond there, too.