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

MADRID/LISBON (Reuters) -Power started returning to parts of the Iberian peninsula late on Monday after a huge outage brought parts of Spain and Portugal to a standstill, grounding planes, halting public transport,

On Monday morning, millions of people across the Iberian Peninsula lost power. The cause of the outage is yet to be determined.