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.

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.

Spain and Portugal declared a state of emergency after an all-encompassing power failure struck those nations as well as Belgium, Andorra and France.