BARCELONA, Spain (AP) — A blackout brought much of Spain and Portugal to a standstill Monday, halting subway trains, cutting phone service and shutting down traffic lights and ATM machines for the 50 million people who live across the Iberian Peninsula.

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.

The cause of the power outage is still unclear, although Portuguese Prime Minister Luis Montenegro says there’s “no indication” of a cyberattack.