Spain and Portugal are racing the setting sun as they respond to a massive, unexplained power outage that knocked out traffic lights, caused chaos on roads and in airports, and threatened to plunge tens of millions of people into darkness on Monday.

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.

The massive power cut that stranded Mr Hughes triggered chaos across Spain and Portugal, and also impacted Andorra and parts of France, from about midday local time (10:00 GMT). Traffic lights shut off. Metros closed. Businesses shuttered and people joined queues to get cash as card payments did not work.