A cross-border power blackout on Monday paralysed the Iberian Peninsula for most of the day, disrupting millions of lives across Spain and Portugal – even interrupting the French electrical system. The sweeping power outage that hit Spain and Portugal this week has raised questions about the electricity grid in a region not normally known for blackouts.

Millions across Europe lost power in a massive blackout. Get the latest updates on affected areas, causes, and more here.

Spain's Prime Minister Pedro Sánchez said Monday that a 'strong oscillation' in the power grid led to the huge outage that struck Spain, Portugal and parts of France, but that the cause was still being determined.