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.

The massive blackout that prompted traffic chaos in the southern European countries is mostly over. The cause of the outage is still unclear.

Spain's national grid operator Red Eléctrica de España has ruled out a cyberattack and pointed to a drop in solar generation as the preliminary cause of the country's power outage, El Pais reports.