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.

The blackout in Spain and Portugal left millions in the dark. Now, details are emerging of deaths that occurred during the power outage. But how many people are dead? What do we know?