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.

States of emergency throughout Spain and Portugal are being lifted on Tuesday, except in Valencia, as the Iberian Peninsula starts to regain power after an unprecedented outage on Monday.  The outage hit Spain,