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.

A countrywide power outage impacted Spain—as well as swaths of Portugal and smaller portions of France—Monday afternoon, affecting essential services and wreaking chaos across the Iberian Peninsula. The cause of the outage is currently being investigated by Spanish and Portuguese officials and ministers.