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 power outage has knocked out electricity across parts of Spain and Portugal, shutting off traffic lights and causing chaos at airports, train stations and on the roads. Follow for live updates.

Power cuts have impacted as many as 50 million people across Spain and Portugal - causing huge disruption to public transport, airports and vital telecommunications networks