A widespread and unexplained power outage knocked out electricity in most of Spain and Portugal on Monday, shutting off traffic lights and causing chaos at airports, train stations and on the roads.

Spanish power distributor Red Eléctrica said that restoring power fully to the country and neighboring Portugal could take 6-10 hours.

A massive power cut hit large parts of Spain and Portugal on Monday, causing widespread chaos and disruption. The outage left millions of people without electricity, while internet and phone networks were also down. Trains were cancelled and evacuated in some regions, traffic lights stopped working amid mounting delays at airports.