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

Spain and Portugal are reeling from a massive, unexplained power outage that knocked out traffic lights, caused chaos on roads and in airports, and prompted both countries to declare a state of emergency.