A widespread power outage hit Spain and Portugal, affecting millions of people who live across Europe's Iberian Peninsula.

The Spanish power distributor calls it “exceptional and extraordinary.” Power went down just after noon and by nightfall only half of the power had been restored in Spain. The cause was not immediately clear Monday.

A massive blackout struck Spain and Portugal, leaving millions without power, disrupting transport and communications, and causing widespread panic. Restoration efforts are underway but the cause remains under investigation.