MADRID (AP) — The cause of Spain and Portugal’s widespread blackouts remained a mystery on Tuesday, with some isolated disruption remaining after power was largely restored to both countries.

Life in Spain and Portugal began to return to normal Tuesday, a day after a massive power outage paralyzed the Iberian Peninsula, leaving governments, companies and experts scrambling to figure out what went wrong.

The hunt has begun for the cause of a massive blackout across Spain, Portugal and parts of France that halted trains, bank machines and traffic lights, in one of Europe's biggest ever power system collapses.