A massive power cut hit large parts of Spain and Portugal on Monday, causing widespread chaos and disruption. The outage left millions of people without electricity, while internet and phone networks were also down. Trains were cancelled and evacuated in some regions, traffic lights stopped working amid mounting delays at airports.

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.

Spain and Portugal are reeling from a massive, unexplained power outage that knocked out traffic lights, caused chaos on roads and in airports, and prompted both countries to declare a state of emergency.