After an electricity blackout plunged Spain and Portugal into darkness, France remained largely untouched. But how vulnerable is the country to such an event? View on euronews

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.

Electricity has returned to most of Spain and Portugal but with continued disruptions on the second day after an unknown failure caused a massive blackout across much of western Europe.