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.

Red Eléctrica, Spain’s electricity grid operator, ruled out a cyberattack, human error or unusual weather. Experts say it could take weeks to determine the cause.

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.