Millions of people across Spain, Portugal, and parts of France were plunged into darkness on Monday following a massive nationwide power outage. The widespread disruption has raised concerns about the stability of the electrical grid in Europe,

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.

Lights flickered back to life in Spain and Portugal early Tuesday after a massive blackout hit the Iberian peninsula stranding passengers in trains