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.

It may take a week for the network servicing both countries to be fully repaired. Meanwhile, millions are without power.

Officials are yet to confirm exactly what caused more than 50 million people to lose power this afternoon, with a number of potential explanations having been offered in the panic