Spain and Portugal began restoring normalcy on Tuesday following a massive blackout that paralyzed the Iberian Peninsula on Monday, marking one of Europe’s most severe power outages in recent years.

While electricity supply has largely resumed, the cause of the disruption remains under investigation, raising concerns about the region’s energy infrastructure resilience.

Spain’s grid operator, Red Electrica, reported that nearly all of the country’s electricity demand was met early Tuesday as the system stabilized.

“All substations are operational,” the company announced on X, signaling significant progress in recovery efforts.

“We keep on working from centre of electric control to secure total normalisation of the system,” it added.

The Madrid underground metro said it has resumed service at 8:00 a.m. local time (0600 GMT), operating at 80% capacity, while Adif, the national rail infrastructure operator, reported that most train services across the country remained suspended.

A massive power outage swept across Spain and Portugal on Monday, plunging millions into darkness and disrupting critical infrastructure in a sudden, nationwide blackout.

The outage, which struck late Monday morning local time, affected both countries, with Portuguese authorities confirming to local media that the blackout was nationwide.